Our Doctors and Practitioners

William L. Diehl
Phone number:

Autonomous University of the State of México, México


General Surgery, Indiana University Medical Center, Indianapolis, IA


General Surgery, Morristown Medical Center, Morristown, NJ


General Surgical Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY

Board Certification:

General Surgery, American Board of Surgery

Hospital Affiliations:

Morristown Medical Center



I am accepting new patients.

Personal Notes:

William L. Diehl, MD, FACS, specializes in cancer surgery of the breast, pancreas, liver, biliary tract, esophagus, colon, rectum, and skin. Dr. Diehl also has expertise in general surgeries, including hernia repair, gallbladder removal, and acute surgical emergencies such as diverticulitis and appendicitis.

Dr. Diehl is among the first surgeons to perform sentinel node mapping — a technique to identify the spread and stage of cancer and help determine the best therapy. At Morristown Medical Center, he performed the first single-site laparscopy (SSL), also known as single-incision laparoscopic surgery (SILS), which is now commonly used to remove the appendix, gallbladder, and sections of the colon. Because it is performed through a single incision in the belly button, single-site laparoscopy leaves no visible scarring. 

In addition to his position with Allied Surgical of Summit Medical Group, Dr. Diehl is a surgical researcher. He is involved in developing surgical techniques with the da Vinci surgical robot that enhance therapy and shorten recovery times. He also teaches in the Morristown Medical Center Surgical Residency Program. He is a member of the American College of Surgeons, American Society of Breast Surgeons, American Medical Association, Medical Society of New Jersey, and Morris County Medical Society. 

Dr. Diehl has practiced privately since 1988. From 2004 until 2009, he was Medical Director of Saint Clare's Hospital Women's Breast Health Center. From 1997 until 2011, he was Director of the Morristown Medical Center Multidisciplinary Breast Cancer Panel. He is Past President of the Morris County Medical Society and American Cancer Society Morris Unit.

Dr. Diehl is a recipient of the Morristown Medical Center John Alkhas Teaching Award and Sharing Village 2007 Annual Humanitarian Award. Each year, he travels to Guatemala City to volunteer his surgical expertise at a medical clinic for the underserved.

Dr. Diehl is featured in the New Jersey Monthly "Top Doctors", Inside Jersey "Top Cancer Doctors," Castle Connolly "Best Doctors in America," Castle Connolly "Top Doctors in the New York Metro Area," and Castle Connolly "America's Top Doctors" listings. Most recently, Dr. Diehl has been featured in the Inside Jersey "Top Doctors for Women's Health" listing for his expertise in breast cancer surgery. Dr. Diehl's Castle Connolly listings have been reprinted in US News and World Report and Inside Jersey.