John Gahagan, MD is a Clinical Assistant Professor of Surgery in the Section of Colorectal Surgery. He has training in advanced minimally invasive surgical techniques including robotic and laparoscopic surgery. He has authored several textbook chapters and original articles in peer-reviewed journals. His clinical practice is focused on the surgical treatment of colon and rectal cancers, inflammatory bowel disease (ulcerative colitis and Crohn’s disease), and benign colon and anorectal diseases (diverticulitis, hemorrhoids, fistulas, fissures). He believes in patient-centered care and multi-disciplinary approach to the treatment of diseases of the colon, rectum and anus. He joined Stanford in 2019 and is excited to build a Stanford colorectal surgery practice in the East Bay at Stanford Tri-Valley in Pleasanton and at Stanford Health Care – Emeryville.

Outside of his clinical practice, he is involved in surgical education and serves as an Associate Program Director of the Stanford General Surgery Residency Training Program as well as the Site Director for the Stanford Tri-Valley surgery rotation. He serves in various administrative roles, including as Chair of the Stanford Tri-Valley Operating Room Committee and a member of the Stanford Tri-Valley Medical Staff Quality Committee and the Stanford Medicine Partners Quality and Credentialing Committee.

Professional Summary

Education & Certifications
  • Board Certification, American Board of Colon and Rectal Surgery, Colon & Rectal Surgery (2021)
  • Board Certification, American Board of Surgery, Surgery (2018)
  • Fellowship, New York-Presbyterian Weill Cornell Medical College / New York-Presbyterian Columbia University / Memorial Sloan Kettering Cancer Center, Colon & Rectal Surgery (2019)
  • Residency, University of California, Irvine, General Surgery (2018)
  • MD, Wake Forest University School of Medicine, Medicine (2012)
  • BS, University of California, Berkeley, Microbial Biology (2008)

Honors & Awards
  • Alumni Scholarship Leadership Award, California Alumni Association, UC Berkeley (2004)
  • Chairman’s Award, Teaching, Department of Surgery, UC Irvine (2018)
  • Dean’s List, College of Natural Resources, UC Berkeley (2004-2008)
  • First Place, Surgical Jeopardy ABSITE competition, Southern California Chapter American College of Surgeons (2016)
  • First Place, Surgical Jeopardy ABSITE competition, Southern California Chapter American College of Surgeons (2017)
  • High Distinction in General Scholarship, UC Berkeley (2008)
  • Leadership Award, Health Worker Program, UC Berkeley (2006)
  • Outstanding Resident Award, Graduate Medical Education, UC Irvine (2016)
  • Stanford Teaching Resource Initiative – ValleycarE (STRIVE) Grant, Stanford University School of Medicine (2020)
  • Student Commencement Speaker, College of Natural Resources, UC Berkeley (2008)
  • Sustainability Ambassador Award, Stanford Health Care (2023)

  • Associate Question Writer, American Board of Colon & Rectal Surgery (2023 - Present)
  • Member, The Association of Program Directors in Surgery (2023 - Present)
  • Member, The Society for Surgery of the Alimentary Tract (2021 - Present)
  • Member, USMLE Step 3 Test Material Development Committee, National Board of Medical Examiners (2021 - Present)
  • Member, Residents Committee, American Society of Colon and Rectal Surgeons (2020 - Present)
  • Member, Young Surgeons Committee, American Society of Colon and Rectal Surgeons (2018 - 2021)
  • Fellow, American Society of Colon and Rectal Surgeons (2016 - Present)
  • Fellow, American College of Surgeons (2012 - Present)

Administrative Appointments
  • Associate Program Director, Stanford General Surgery Residency Program (2022 - Present)
  • Co-Director, Stanford Tri-Valley Clinical Academy (2021 - Present)
  • Member, Clinical Competency Committee, Stanford General Surgery Residency Program (2021 - Present)
  • Member, Operating Room Committee, Stanford Tri-Valley Medical Staff (2020 - Present)
  • Member, Quality and Credentialing Committee, Stanford Medicine Partners (2021 - Present)
  • Member, Quality Committee, Stanford Tri-Valley Medical Staff (2022 - Present)
  • Member, Resident Selection Committee, Stanford General Surgery Residency Program (2021 - Present)
  • Site Director, Stanford ValleyCare General Surgery Elective, Stanford General Surgery Residency Program (2021 - Present)


Clinical Trials

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Practice Locations

Gastrointestinal (GI) Cancer Program in Pleasanton Pleasanton, CA
Pleasanton, CA

5725 W. Las Positas Blvd., Suite 100

Pleasanton , CA 94588

+1 (833) 444-7622

Make An Appointment More Clinic Information » Getting Here »

Cancer Center in Emeryville Emeryville, CA
Emeryville, CA

5800 Hollis Street

Emeryville , CA 94608

+1 (833) 444-7622

Make An Appointment More Clinic Information » Getting Here »

Gastrointestinal (GI) Cancer Program in Emeryville Emeryville, CA
Emeryville, CA

5800 Hollis Street

Emeryville , CA 94608

+1 (833) 444-7622

Make An Appointment More Clinic Information » Getting Here »

Patient Ratings

(68 Ratings)

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Patient Reviews

(55 reviews)

Dr Gahagan is fantastic! Always kind, very informative and consults with everyone on the team.
explained things very well
I feel Dr Gahagan is knowledgeable and seems to care about his patients.
He was great. Thank you.
John Gahagan is very caring and understanding to my situation. He listens well and seems to really care a lot and is very professional.
Dr. Gahagan is clear, concise, and honest. Very knowledgeable and has the patient’s best interests in mind. Always wants to know if you have thoughts, questions or concerns. I appreciate his care and soft sense of humor in nervous times. Had a fantastic first procedure, and grateful to be in his care for this second, and hopefully final, procedure. I am eternally grateful to have been treated by him.
I was very pleased with my visit with Dr. Gahagan. He is an outstanding physician and surgeon. Patients, like me, are extremely fortunate to be under the excellent care of a highly qualified doctor of medicine. Dr. Gahagan is a praiseworthy member of Stanford Health Care.
Excellent surgeon who I would highly recommend to others.
I am very greatful to have Dr Gahagan. He provides detail explanations, transparency and is very thorough with his answers. I would highly recommend Dr Gahagan to others.
This doctor was very informative and kind I appreciate him taking his time with me
Excellent service
Dr. Gahagan listens.
Excellent and informative visit. Explained the issues, diagnosis and options clearly and completely
excellent doctor, explained things very well. Very professional, kind and caring staff.
My husband and I were VERY impressed with Dr. Gahagan's professionalism, knowledge and bedside manner. He answered ALL of our questions and reassured use. We are grateful we were referred to him by Dr. Manthruium. Wish I would have seen him in August! Thank you Dr. Gahagan!
I appreciate the care and knowldge that Dr. Gahagan brings to his practice.
He was very Professional but kept it very real
Dr. Gahagan explained every details that I had to know and be aware of. He's an excellent doctor.
I am confident in Dr. Gahagen’s abilities. He dies not rush me and answers all my questions. I feel very comfortable with him.
Very thorough examination
Very professional and knowledgeable Doctor
Very good doctor and staff, responsive, nice folks
He was very thorough and I’m very happy I was able to have a video visit with him as it’s very inconvenient for me to come to his office.
Very professional.
Dr was very awesome
Dr. Diagnosed my issue and resolved it with surgery. He was great
Made you feel comfortable and ease
Amazingly patient !!!!! Gold stars in his crown !
Very patient oriented; explained in detail risks and benefits of surgery; took time to answer all questions. Very compassionate.
Very professional and yet very personal
excellent surgeon
Dr. Gahagan is the absolute best! He has been on top of my condition since the very first appointment! As well as his expertise in my condition he has always gone beyond the norm in follow up as well as being very gentle & kind!
Excellent Physician and certainly conscientious about best practices for patient care.
John Gahagan is an outstanding doctor. He went above and beyond in his care of me - returning my call during his vacation to address my medical concerns post-surgery. He's an excellent communicator. He listens deeply and responds respectfully, scientifically, and with clear instructions. I felt safe, confident, and genuinely cared for from our first video visit to the last. I wish every doctor were like him!
Dr. Gahagan answered my my questions fully. Very helpful and kind.
Thank you for seeing me today, and the referral to Women’s Health Center.
It is always pleasure to see him because he is caring, sensitive, and concerned with my well-being. I am very greatful that I found such a fabulous surgeon. I want to thank him for being on time.
Dr. Gahagan just purely "AWESOME "!!!
Kudos to you sir you are Very knowledgeable kind .. You always go the extra mile. You're such a gentleman. Thank you for Listening to me the patient . I am grateful that you have a lot of wisdom and discernment about the concerns and the wishes of the patient. Grateful to have you as a team leader. Thank you so much Dr. John Gahagan..
Dr Gahagan is absolutely wonderful! He is the first physician that I saw concerning my issue and he has continued to monitor my treatment. He is always on top of my case! His expertise is also top notch! I am so happy that he is my doctor!
Dr. Gahagan is very professional and does an excellent job of making sure me as a patient understands the treatments and risks and is very good at prompting for any questions that might be of concern. I am very confident of the care I am being provided by Dr. Gahagan and all of the Stanford staff.
Dr. Gahagan was a joy to meet and have as a caregiver. He was attentive and thorough in his care. He will be my choice in the future if I should ever need his services.
He’s the best of the best
Very good! Explained everything to me.
excellent experience..
Excellent doctor/surgeon.
Dr. Gahagan was knowledgeable, thorough, respectful, and answered all my questions... good LISTENER.
Dr. Gahagan has been the absolute BEST! From the 1st visit where he indicated that I had a "mass" and with his communication since then. He has also expedited my diagnostic treatment and referrals for my treatment.
This is a great location it's clean, very friendly staff (all in general).
The doctor called at home after we returned to Chico expressing concern. This was several hours later and he followed up with concern for my wife. I believe he went over and above to care for a patient. Very commendable!!
Dr. Gahagan was amazing - His explanation of everything was always clear, thorough and concise.
Dr. Gahagan is one of the 'best' dr.'s I have ever met. He is compassionate, caring, and 'never' rushes through any interaction. I highly recommend Dr. Gahagan!!!
The physician was patient and shared his knowledge in terms I understood so I could help in making the right decision fir my situation,
Again, nothing resolved, nothing done to help w/pain or assistance to help me feel better. Conclusion was I was constipated.

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