modern medicine with old fashioned service

Quality medicine with honesty and affordability

About us

Welcome to Alton Main Animal Hospital!

Since 1986, Santa Ana, California area has known Alton Main Animal Hospital as the place for dedicated care for the other family memeber. We try to approach every case with every patient as if that patient were our own pet. We also believe that prevention of disease is far better than treatment of a disease that could have been prevented. Therefore, we emphasize puppy and kitten care programs, annual exams, wellness blood profiles, and appropriately scheduled vaccines and parasite control. We have a well-equipped surgery suite for general, orthopedic, and cosmetic procedures, with emphasis on pain prevention and control. We offer reasonably priced spays and neuters that include multi-system anesthetic monitoring, absorbable sutures, and post operative pain management. We also Emphasize good dental health for middle-aged and senior pets.
Dr. Isaac Shim

Dr. Isaac Shim, DVM

Dr. Shim earned his veterinary degree from Seoul National University in Seoul, Korea in 2001 and completed advanced education and clinical training at Cornell University Hospital for Animals in Ithaca, New York in 2004.

He then worked at many general practices, overnight emergency hospitals, and 24-hour specialty hospitals in Arizona and Southern California before joining Alton Main Animal Hospital in 2010.

Dr. Hong Moon, DVM
Dr.Efren Zuniga, DVM

Dr. Moon and Dr. Zuniga were co-owners of Alton Main Animal Hospital from 1986 to 2017 before Dr. Shim took over the sole ownership of the hospital in 2017.

They have been still working here as associate doctors.

Our Doctors

Our goal is to help you in any way we can keep your pet as healthy as possible and help you keep your relationship with your pet an enjoyable one.


About Alton Main Animal Hospital is proud to offer


Hear what our clients have to say

Thanks to Dr. Shim and staff...
I am thoroughly impressed and extremely thankful for the recent care that we received for our 11 week old puppy, Izzy. Dr. Hyung Shim is amazingly caring and professional. He explained the problem in "layman" terms and the various choices of treatments. We were allowed to ask as many questions as we had and we never felt that he was rushed for time or brushing our concerns aside. He actually listened to us! He was available to talk to when we called to check on her while she was in the hospital and he PERSONALLY called to check and see how we were doing after we had her home. The staff was friendly and informative -- at the front desk, Malia was a joy to deal with even in our "stressed" condition.
Pamela & Jim Preston
The vet I'd trust...
Dr Shim is now the only Vet in Orange Cnty that I'd trust with the care of my animals. He is knowledgable, gentle, caring, and concerned with not only the health of my cats but also with the cost of caring for them. He and his team are excellent practictioners. I now take my pets to Alton Main for their annual shot regimens, their baths, flea treatments, food, and emergency care. Recently, one of my older cats was suffering from the lingering effects of a kidney disease. Dr Shim ran a series of tests that uncovered an additional problem - and the animal is now receiving treatment for a thyroid condition that had gone undetected by their former Vet. The prognosis for her recovery is good. I am very grateful for Dr Shim's attention to details and his insistence on thoroughness.
Rick L.
Alton Main Animal Hospital is SUPERB~~
We recently had our sick dog Jolly treated at this hospital by Dr. Hyung Shim and he was a SUPERB physician! Jolly had been demonstrating intermittent problems with breathing. He listened (really listened) to the symptoms that we told him that we had observed and he asked very good questions. He did an extensive assessment (blood,urine, xray) - very thorough! Once he had the results - he gave us his diagnosis/opinion in a very honest manner. He gave us numerous options as to what he thought would be best for Jolly. We took Jolly home and on the ride home we had more questions. I called him and he talked with me for some time and he gave me referrals to specialist hospitals and he sent me the xray via e-mail so that we could get assistance over the weekend as we were really worried about his condition - not knowing if he would get worse - or if we had seen the worst of it. The following day Dr. Shim was kind enough to continue to assist us - even though it was his day off! He demonstrated his intelligence, compassion, and good common sense with the advice that he gave us. We followed his advice and took him to a specialist hospital and we are SO GLAD that we did as Jolly is better - back playing with his buddy Sparky. Alton Main Animal Hospital is SUPERB! I would rec-commend this hospital to every animal/pet lover in the world!!! We will continue taking Jolly and Sparky there - that is for sure!!!! We love you Dr. Shim - and we love the entire staff - you are all AWESOME!!!! I have one question for those of you reading this do you REALLY thank someone for saving your pet's life?
Deb Black-Ralston

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