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. Julie Abrams


Dr. Abrams graduated from Union College in New York with a Bachelor’s of Science degree, and she received her DVM from the Ross University School of Veterinary Medicine in St. Kitts (2011). She grew up in Texas but also has lived in upstate New York, Ohio, Boston, and San Diego. Dr. Abrams is now happily settled in the Bay Area. She is married with a young daughter, and the family has the two cutest rescue pups: Tim and Lincoln. According to Dr. Abrams, “My areas of special interest are gastrointestinal disease and dentistry. I love being a part of Geary Veterinary Hospital, and my favorite aspect is its long-standing history with the community. Generations of clients bring their pets to us!”

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.”



Operations Manager

Tara is Geary’s Operations Manager, with a background in customer service and recruiting. She graduated cum laude with a bachelor’s degree in sociology from San Francisco State University. Tara and her partner Dave live in Oakland with their three pets, all rescues. “Baxter is our Chihuahua mix and is almost 15 years old, Dito is our Formosan Mountain Dog mix from Taiwan, and Quasimoto is our Sphynx (hairless) kitty. Bax is the troublemaker and even at his senior age is full of mischief.” Tara and Dave enjoy hiking and camping with their pets. Her favorite part about her job is striving to provide the best care at all times, while working alongside people who care deeply about their patients and the well-being of animals.

Patient Care Team


Veterinary Technician & Patient Care Specialist

Joel has been with Geary Veterinary Hospital for more than a decade. He graduated from Cuesta College in San Luis Obispo with associates degrees in both science and art, and a degree in construction management (he holds a general contractors license in California). Joel attended the Veterinary Allied Staff Education (VASE) program and is now a nationally registered Veterinary Technician. “What I enjoy most about working at Geary are the challenges offered by veterinary medicine, as well as being able to learn something new every day.” In his downtime, Joel likes hiking and walking. He’s engaged to be married to Melissa, who also works at Geary.


Veterinary Assistant 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.”


Veterinary Technician & Patient Care Specialist

Melissa graduated from Veterinary Allied Staff Education (VASE) and is a registered Veterinary Technician, as well as Geary’s Safety Manager/Coordinator. Animals are Melissa’s passion. “I love client education and interacting with pet owners and pets. After a hard day’s work, I know that I have benefited and improved animals’ lives. At Geary, I love to organize and decorate. Decorating the hospital for the seasons is my thing!” Melissa has a parakeet named Seamus and a fancy goldfish, plus lots of houseplants. She enjoys hiking, exploring, attending car shows, and knitting, and she’s a self-proclaimed tiki fanatic. (She even has a tiki tattoo.) And in case you haven’t heard the news, Melissa is engaged to fellow employee Joel.


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

Breanna went to school to become a Veterinary Assistant and has been learning on the job at Geary Veterinary Hospital. She says, “I’ve learned so much here, and it’s been a real pleasure getting to know everyone. I’ve made some great friends and truly enjoy being a part of such an amazing team.” A former dog walker/sitter, Breanna has three dogs of her own: Cali, Buddy, and Duke. She also has a cat named Stanley and two other kitties, Chai and Lilo (a.k.a. L.L. Cool Ranch), that she adopted from Geary clients. Plus, she has a crested gecko. In the past, Breanna owned snakes, lizards, frogs, ferrets, and exotic fish. In her free time, she enjoys playing video games and working on her 2013 Subaru WRX STi (her pride and joy). She and her boyfriend like to go camping in the summer and snowboarding in the winter in Tahoe.


Veterinary Assistant

Chelsea is a student at Santa Rosa Junior College, on her way to becoming a Registered Veterinary Technician. She has worked in the veterinary field and with marine mammals, as well as with horses, serving as a wrangler/trail guide in California and other states. She grew up with many pets, including dogs, cats, lizards, and rabbits. She currently has three cats and two dogs, and hopes to someday have horses. Chelsea and her boyfriend (a member of the Crockett Volunteer Fire Department) both participate in the Scottish Heavy Athletics, part of the Highland Games, attending about ten events a year in Northern California, including the strength and throwing events. Chelsea is also a crochet addict and enjoys crocheting gifts for people/pets (including those at Geary). She says, “The owners, staff, clients, and climate of Geary Veterinary Hospital are absolutely amazing. I have never worked somewhere so welcoming and caring.”


Veterinary Assistant

Michael recently graduated from Washington State University with a Bachelor’s of Science degree in Zoology, a minor in Chemistry, and a certificate in Molecular Biosciences. He was an undergraduate intern at the WSU Veterinary Teaching Hospital in both the large and small animal clinics. Michael first began working at Geary Veterinary Hospital in the summer of 2019 and during his school breaks. He comes from a family of seven and has four older sisters, and he loves when they all get together for holidays and vacations. At home, Michael has four cats (Tiger, Lily, Posey, and Willow) and a Golden Retriever named Shelby. Michael is a swimmer and was a part of the Indian Valley Swim Team in Walnut Creek for 15 years. He loves the Walnut Creek community, saying: “I like working with all of our clients, especially when I run into friends and family who come to us with their pets. Everyone at Geary always laughs because at least once a day I recognize a familiar client who comes in. The staff here is so fun to work with.”


Veterinary Assistant

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.


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.

Client Service Representatives


Client Services Representative

Grey recently moved back with her family in North Carolina. She is helping us remotely, which we are very excited about. Grey is responsible for appointment scheduling and client education, and helping pet owners learn about vaccines, preventative medications, and puppy protocol. She graduated from UNC Wilmington and worked at a veterinary hospital in Raleigh, North Carolina, before moving to the Bay Area in 2018. Her rescue mix, Raleigh, is part Catahoula Leopard Dog. He was found on the side of the road when he was only five weeks old. Grey’s favorite part of working at Geary is representing something she believes in: high-quality veterinary care from a kind and knowledgeable staff. “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 100 percent believe in the work we do here.” We are thrilled she can help our clients even from across the country!


Client Services Representative

Margaret enjoys coming to work each day to help all of Geary’s clients have the best possible experience for themselves and their much-loved family members. She is thankful for all the support she receives from the doctors and her fellow employees. In her own words, “I always had many animals growing up, and I knew I wanted to work with them in my everyday life. I started my career as a client services representative in 1986 and loved it from the first day. I left that job four years later to raise my three children. Puppies are much easier than teenagers!” All of her children share her love for animals. Margaret has a “sweet, crazy, fun” little rescue kitty named Lola to come home to each day.