Our caring and compassionate veterinary care team.

Meet the Veterinarians and Team of Geary Veterinary Hospital in Walnut Creek. We’re pleased to provide exceptional veterinary care for your pets. Please call us at (925)-938-8010 to speak to one of our caring staff members.

Dr. Gillian Hamilton


Dr. Hamilton graduated from Mount Holyoke College in Massachusetts with a Bachelor’s of Science degree in Biology (1996) and from Emory University Rollins School of Public Health with a MPH in Epidemiology (2000). Before deciding to become a veterinarian, Dr. Hamilton worked as an epidemiologist at the Centers for Disease Control in Atlanta, Georgia, and then as an infectious disease epidemiologist for the Massachusetts Department of Public Health in Boston. She moved to California in 2003, where she eventually attended UC Davis School of Veterinary Medicine and met Dr. Weiss. After graduating in 2008, Dr. Hamilton completed a rotating internship at San Francisco Veterinary Specialists and then joined the team at Geary Veterinary Hospital, where she stayed for five years before moving to St. Thomas, Virgin Islands. She later returned to California to be closer to family and pursue a future as a business owner.

Dr. Hamilton understands the unique human-animal bond, and in her efforts to provide the best possible care for each individual, she works hard to get to know every client and patient. This new chapter in Dr. Hamilton’s life is especially exciting because she loves being back in California and embracing the challenges of small-business ownership with Dr. Weiss. In Dr. Hamilton’s words: “I’m grateful to Dr. Bjork, who established Geary Veterinary Hospital back in 1979, served so many families and pets for nearly 40 years, and then made plans to hand off the business to us as he eases toward eventual retirement. Dr. Bjork’s leadership has been invaluable, and I look forward to helping build on Geary’s success while taking the business into the future.”

Dr. Hamilton lives in Orinda with her husband and their son, as well as a cat named Flair and a rescue German Shepherd called Roxy. Clients of Geary may have seen her son around the office, where he enjoys chatting with clients and staff, shredding documents, and learning about the business.

Dr. Erica Weiss


Dr. Erica Weiss-Laroche graduated from Bucknell University (Lewisburg, PA) in 1998 with a Bachelor’s of Science degree in Biology. After college she worked in research, analyzing human and veterinary pharmaceuticals and biomedical devices. Dr. Weiss moved to California in 2002, and in 2008 graduated from UC Davis School of Veterinary Medicine. Four years later, she completed a residency in Laboratory Animal Medicine at UC Davis. She began working with Dr. Bjork in 2015 when Dr. Hamilton moved to St. Thomas, Virgin Islands.

Dr. Weiss lives in Vallejo with her husband, who is a physician in Occupational Medicine. He also coaches sled hockey, an adaptive sport for children with disabilities, for the Bay Area Outreach Program (BORP). Dr. Weiss and her husband have a young son, who plays hockey and soccer—and loves scary movies. The family has four Devon Rex cats named Elsa, Ana, Giacomo, and Scooter.

Dr. Weiss’s dream was to own a veterinary practice, and she was thrilled to partner with Dr. Gillian Hamilton whom she met at UC Davis. “Gillian and I got to know each other on our very first day of vet school. I sat down next to her, and we’ve been friends ever since! We feel so fortunate to have gone from friends and study partners to co-owners of a well-established veterinary practice, and we look forward to the journey ahead.” Dr. Weiss has worked with a variety of animal species including cats, dogs, guinea pigs, mice and rats, rabbits, pigs, and sheep.


Dr. David Bjork


Dr. Bjork was raised in Berkeley and attended UC Davis as an undergrad. He graduated from Washington State University Veterinary School in 1969. He returned to the Bay Area after veterinary school and worked in Oakland. Dr. Bjork had the honor of working with dermatology expert, Dr. George Muller at Muller Veterinary Hospital in Walnut Creek. After several years at Muller’s, Dr. Bjork and his wife Kim opened Geary Veterinary Hospital in 1979. Dr. Bjork and Kim have two children who worked with their dad when they were younger. Dr. Bjork and Kim sold the practice in 2018 to Dr. Hamilton and Dr. Weiss. Dr. Bjork sees patients three days a week and follows his passion for skiing the other days of the week. He has one Frenchie named MoMo.

Dr. Nathalie Petersen


Dr. Petersen grew up in Atlanta, Georgia, and spent her summers in rural Michigan, where she developed a love for animals and nature. Her mother (a doctor) encouraged her daughter to choose a career that would allow her to find joy in her work. It only made sense to pursue her dreams of becoming a veterinarian! She graduated from Michigan State University in 2006 with a Bachelor’s of Science degree in Environmental Biology and Zoology. She received her DVM from Louisiana State University in 2011 and has lived in the Bay Area since 2018. Dr. Petersen appreciates the variety that being a general practitioner brings. She is a Contra Costa Veterinary Medical Association board member and is Fear Free and PennHip certified. At Geary, she looks forward to forming lasting relationships with both the clients and their pets throughout every life stage. Outside of work, Dr. Petersen loves spending time with her long-term boyfriend and their three terriers: Maverick, Biff, and Ziggy Stringcheese. Her favorite activities include hiking, running, reading, and traveling.

Dr. Mary Ann Wickes


Dr. Wickes has been a veterinarian at Geary Veterinary Hospital since 2000. She received her veterinary degree from Cornell University in New York and returned to California for an internship at Santa Cruz Veterinary Hospital. She then spent five years in emergency medicine in the East Bay, returning to daytime practice after she started a family. Dr. Wickes and her husband, whom she met at Heather Farm swimming pool, live in Walnut Creek and have three grown children and two young grandchildren (so far). The entire family has been involved with competitive swimming and/or triathlons for many years. Today, Mary Ann is still a member of the Walnut Creek Masters swim team, along with their two local children. Dean and son Greg also coach the UC Berkeley triathlon team. The family has two cats, Oscar and Otter, and two grand-dogs: Doris, a French bulldog, and Tucker, a Golden Retriever.

“After so many years in practice, I still love what I do. Getting to know our clients and helping their pets in the best way I can is what makes my career fun and rewarding every day.”

Dr. Kenichiro Yoshida


Dr. Yoshida grew up in Castroville, California—the artichoke capital of the world!—and started his training as a veterinary assistant throughout his high school and undergrad years. He graduated from CSU Fresno with a Bachelor’s of Science degree, focusing on pre-veterinary medicine. He then worked for several years in biomedical research, where he first met Dr. Weiss. In 2016 Dr. Yoshida earned his DVM from Purdue University.

Dr. Yoshida practiced mixed-animal medicine in Humboldt County before he and his wife moved to the San Francisco Bay Area to be closer to family. He’d like clients to know this: “I’m Fear Free certified, and I’m excited to be part of the Geary Veterinary Hospital team. I will bring my thoroughness, compassion, and care to every patient that I meet.”

In his free time, Dr. Yoshida enjoys baking (his specialties are chocolate chip cookies and sourdough bread), practicing his guitar, playing ice hockey, and catching up on TV shows with his wife on the weekends. Dr. Yoshida completed his first half-marathon in 2021 and is currently in training for his next one. He and his wife like to spend time with their dog (Princess) Leia, who doesn’t understand the meaning of no when asking for scratches and petting.



Clinical Manager

Before she arrived at Geary in 2012 where she started as a client services representative, Karen always knew she wanted to work in a field dedicated to animals. She is the youngest of seven children and grew up with many pets, so her love for animals and her interest in their welfare came at a young age. In 2017, she volunteered to help with animal care at both the Houston Society for the Prevention of Cruelty to Animals (SPCA) after hurricane Harvey and at the Tubbs Fire in Sonoma. While working at Geary Veterinary Hospital, Karen cross-trained to join the patient-care team and went to school to become a registered Veterinary Technician. She has two senior dogs, Niño and Dollie, who are her “special-needs kids, and pride and joy,” as well as two rescues, a German Shepherd (Coraline) and a Lab mix (Athena). As Karen says, “There is so much I like about working at Geary but mostly it’s that all of the people here are like my second family.”


Lead Client Services Representative

Kristin is in charge of scheduling appointments, filling prescriptions, answering phones, and helping to ensure clients get the best care for their pets. She says, “I love coming to work at Geary Veterinary Hospital every day. Whenever I walk through the door, I know I’m surrounded by smart, hard-working, and compassionate people.” Kristin has over five years of experience working in the veterinary field, both in private practice and in shelter medicine. She particularly loves private practice because she gets to follow patients through every stage of their lives. At home, Kristin has two pets: Kittums (an eighteen-year-old cat) and Freckles (a rescued Chihuahua mix who at age thirteen still acts like a puppy). Kittums spent years traveling the West Coast with Kristin and her husband and is never shy about her feelings. She often informs the neighborhood of her mood by loudly meowing in the backyard at certain times of day. Kristin is happy to report that Kittums and Freckles have become best friends, although it took years for that to happen and Kittums still tries to hide it!


Veterinary Assistant Supervisor

Miriam says, “I really love working at Geary Veterinary Hospital. The owners, Gillian and Erica, go out of their way to make sure that every patient’s quality of life is the first priority. All of my coworkers show genuine care for our patients and are always there with a helping hand.” Miriam began at Geary working at the front desk, greeting patients and their owners and prepping rooms for appointments. She has had some schooling at Carrington College in Sacramento in the Veterinary Technician program. A few months after working at the front desk, she began cross-training to work with Geary’s patient care team. She is now a Veterinary Assistant helping to care for patients. Her education, as well as her hands-on experience with animals, has led her to pursue advancing her skills so she can eventually become a registered Veterinary Technician. Miriam and her husband share two beautiful kids and are the proud owners of three cats. Her family loves staying at home but also enjoys outdoor activities such as hiking, bike riding, and camping.

Patient Care Team


Veterinary Assistant

Alfonso—also known as Poncho—joined Geary Veterinary Hospital in 2018 as a Veterinary Assistant. “Funny story: I showed up, thinking I had a job interview. What happened was a different clinic had left me a voicemail that sounded like ‘Interview Geary Hospital.’ Upon arriving at Geary, I said I was here for my job interview and the receptionists looked confused. I realized I was at the wrong place. But I was lucky enough to be interviewed anyhow, and I got the job!” While growing up, Alfonso spent time on ranches and was a member of 4-H, which inspired his passion for animals. He has helped manage livestock herds, participated in livestock showmanship breeding programs, and worked with African Savannah animals at Safari West in Santa Rosa. Before joining Geary, Alfonso worked for a year in Northern Ireland, where he helped promote tolerance and diversity, and traveled to fourteen other countries. He enjoys hiking, dancing, and taking road trips, or simply staying home with his 16-year-old Chiweenie, Spikey. Alfonso also volunteers with a local youth-empowerment organization, One Day At a Time.


Veterinary Assistant and Client Services Representative

At the beginning of the pandemic, Jensen left his job as a receptionist at a wellness center to become a veterinary receptionist. His plan was to gain animal-care experience from the ground up, with the goal of becoming a veterinary assistant. In the past, Jensen had stocked shelves and cared for animals in a pet store, as well as doing pet-sitting for friends and family. Now, after working at Geary Veterinary Hospital for a time, he aspires to take courses to become a registered Veterinary Technician (RVT) and also work with exotics and domesticated farm animals someday. “I learn new things on the job every day alongside bright, warm-hearted people whom I respect and appreciate for their patience with me. I’m forever grateful they took a leap of faith on me as someone newer to the field. I look forward to having more fun, memorable moments with the Geary team, our patients, and their pet parents. Here, I’m given the space to be myself, as well as my best self!”

Jensen comes from a big family that’s spread apart location wise—six siblings and ten nephews and nieces. At home, Jensen has a cat that is essentially his child (and she knows it). Her name is Zenith and she’s Jensen’s world. He also has a leopard gecko named Fernando and a mountain king snake named Kaien. For fun, Jensen enjoys movie nights with friends, going on hikes, cooking delicious food, painting, playing video games, and dancing.


Registered Veterinary Technician

Kayla knew from a young age that she wanted a job that involved caring for animals. Too many times she’d talk her grandma into helping stray animals and of course keeping them! After Kayla graduated from high school, she started the Veterinary Technician program at Carrington College in Pleasant Hills and two years later received her Associate degree in Science in Veterinary Technology. She passed the Veterinary Technician national exam and the California state exam in 2017. In Kayla’s words, “I was so proud of this accomplishment after all my hard work! After college, I spent time in a general veterinary practice but then went into veterinary dermatology for nearly five years. Although I enjoyed animal dermatology, I felt it was time to come back to general practice and continue to increase my knowledge in this setting. I really enjoy surgical preparation and giving supportive care to the fur babies.” Kayla lives with her husband and toddler daughter, and together they love to go to the park, take walks, and sing/do silly dancing. Kayla also loves being part of Geary where every day—even the toughest days—the team works together to get the job done.


Veterinary Assistant

Martha says, “Everyone here has welcomed me since the beginning. They have been super amazing and make me feel like work is my second home. The best part of being a Geary team member is the people who work with me. I’m grateful for the dedication that all the doctors and staff show each day.” Martha assists with many tasks, including surgery prep, helping with diagnostics (blood draws and Xrays), and doing laser therapy on patients. She has been in the field for five years, starting in Richmond, California, where she was a lead Vet Tech. In 2017 Martha graduated from Pima Medical Institute in Albuquerque, New Mexico, where she received her Veterinary Assistant certificate. She earned her Associate degree in Integrated Studies in 2015 from Central New Mexico Community College. Martha lives in Concord and is currently a student at Penn Foster College online. Aside from studying all the time, Martha loves being with her family (husband Manny and young son Dante) and her pets (two dogs named Raiden and Loki).  Dante loves playing with the dogs, especially catch with Raiden. Dante’s first giggles were with Loki when he sneezed!


Veterinary Assistant

Nicole (Nic) was born and raised in the San Francisco Bay Area. Because of her love for animals, she has worked with East Bay Animal Rescue & Refuge (EBARR) and performed animal-husbandry jobs at wellness/vaccine clinics, pet-boarding places, and ranches. “At Geary, I enjoy establishing connections not only with our animal patients but also with their human owners. As caretakers and animal professionals, we are these animals’ voices. I will always strive to do my best to help meet the needs of pets and their human counterparts alike.” Nic plans to apply to the Veterinary Allied Staff Education (VASE) program to become a registered Veterinary Technician. In her free time, she loves to hike and take photographs. Her main pastime is taking care of her horse Delilah.


Veterinary Assistant

Taylor graduated from California Polytechnic State University in 2022. When she was a student, she volunteered at the Cal Poly Cat Program (which finds forever homes for cats), interned at the Oakland Zoo, and worked at an animal sanctuary called Happy Hen in San Luis Obispo. Her job at Geary includes taking vitals, helping prepare for surgery, performing laser therapy, and assisting in blood draws, urine collection, and radiographs. Taylor is interested in eventually becoming a Registered Veterinary Technician (RVT). “Having such a kind and dedicated staff to spend workdays with makes me strive to be the best I can be for our clients and their pets. My family has three cats whose names are Nibbles, Little Dude, and Mimosa (Mimo, for short). I also own two cats with my boyfriend: Klay and Kiwi. I love hiking, traveling, watching movies, playing video games, and hanging out with my kitties. My favorite animal is and always will be a cat!”

Client Service Representatives


Client Services Representative

Brianna attended College Park High School and is a student at Diablo Valley College, where she majors in the performing arts to pursue her dream of someday becoming an entertainer. According to Brianna, “It’s always been just me and my mom, but I wouldn’t trade it for the world. Our first pet was a cat named Moonlight, who we recently lost, but will always be my baby girl. I also had a mini poodle mix named Beethoven and was lucky to have loved him. My family has recently welcomed two new kittens into our lives, Binx and MooMoo. I’ve run my own pet sitting/dog walking business for over five years now, and it’s a perfect way to get close to lots of animals. Every pet I spend time with is incredibly special. I have past veterinary experience, previously working at an emergency clinic as part of the client-care team. Finding my way to Geary feels like it was meant to be. This is a group who treats each other like family, and that extends to the clients and patients we serve as well!”


Client Services Representative

Krista graduated from College Park High School and Diablo Valley College with an Associate degree in Art for 3D Modeling and Animation. She worked at Petco for four-and-a-half years, learning about nutrition and petcare, ranging from aquatics to small animals to cats and dogs. At Geary she helps clients with whatever is needed for their pet, whether it’s appointments, medications, or vet records. Krista grew up surrounded by cats but has to admit she loves dogs more, with the Great Dane being her favorite breed. After losing her 21-year-old cat Simba, Krista has one kitty, a domestic shorthair named Nala, who’s still a little skittish. In her free time, Krista likes to play video games and read (if she’s not doing one, she’s usually doing the other). She also has a 20-gallon aquarium! Her fanciest friend in there? An angelfish. “What sets Geary apart from my other jobs—especially corporate jobs—is the smaller employee size and more caring management style. I enjoy the sense of togetherness and know I’ll get genuine help when or if it’s needed. I love how close and accepting everyone is. No one is made to feel left out at Geary (humans and pets alike).”


Client Services Representative

Mary is a Bay Area native and has always had a soft spot for caring for animals. Her background is a little uncommon in the veterinary world, as she has a degree in cosmetology (from the College of San Mateo) and is a licensed cosmetologist. After the pandemic and ten years spent in the beauty industry, Mary wanted to find a job that allowed her to express more empathy, offer genuine care to clients, and help people (and pets!) feel appreciated. “I was encouraged to apply to Geary because of a roommate. Funny story: I’d always hear about how much fun he would have at his job and that it was hard work but fulfilling. I just had to apply as soon as I heard there was a CSR opening! Now each day I’m awed by how sweet our clients can be. The doctors and staff are wonderful and offer amazing care.” Mary doesn’t have any pets of her own at the moment, but she’s a proud “Auntie” to her older brother’s pets—a very reserved yet loving Siamese cat named CC and a gorgeous, playful Maltipoo named Bella. Outside of work, Mary likes to see live performances and concerts, enjoy the arts, and help out with the occasional makeover for a special occasion.

Virtual Care Coordinator


Virtual Care Coordinator

Grey began working at Geary in 2018 as a CSR, but now lives in San Diego and works with us remotely. Grey is responsible for our online services, including appointment scheduling and client education. In her free time, Grey loves attending baseball games and taking her rescue dog, Raleigh, for walks. Raleigh is a Catahoula Leopard Dog who loves tennis balls and (unfortunately) dislikes humans. Grey’s favorite part of working at Geary is representing something she believes in: high-quality veterinary care from a kind and knowledgeable staff.  In her words, “People ask my opinion of Geary Veterinary Hospital all the time. The most important thing to me is being able to tell them that I believe in the work we do here and that our staff is offering the best possible care.” We are thrilled she can help our clients even when she can’t be here with us in the hospital!

Blog Contributor and Graphic Designer


Blog Contributor and Graphic Designer

Ali grew up in Cleveland and went to college at Indiana University, receiving her Bachelor of Fine Arts in 2009. She moved to the Bay Area in 2012. At school, she enjoyed not only her art and design classes but also courses in anatomy, physiology, and medicine. The pandemic gave Ali an opportunity to look inward and consider her career possibilities, her sense of purpose, and her wish to be of service to others. She joined Geary in the fall of 2021 as a Veterinary Assistant/CSR, while also using her design skills to help in whatever capacity needed.

In late fall 2022, Ali moved to New Bern, NC to be closer to family. Despite moving across the country, Ali continues to work in the veterinary field as a veterinary technician assistant at Craven Animal Hospital in New Bern, and as a blog contributor and graphic designer (working remotely) for Geary! 🙂 Be sure to check out The Doctors’ Blog and some exciting new features coming to our website! 

Ali credits her Basset Hound—Bowzer—as one of her main inspirations to embark (pun intended) on her journey into the veterinary field. Bowzer is quite the character and the light of Ali’s life, even when he’s being a bass-hole.

Ali says: “It’s rewarding to know I can be an advocate for animals, those who don’t have a voice. I love to be of service through client education and helping the patient-care team. The people here at Geary truly value each employee as an individual, making the hospital feel like a supportive community where we all contribute. I’ve even found opportunities to use my design background to help the hospital with graphics, charts, the new blog, and more. It’s a win-win.”