
J. Mark Barnett, MD
Medical Oncologist / Hematologist
Provider Biography
Dr. Mark Barnett is board certified in medical oncology and hematology. He completed his fellowship training at the Brown University program in Providence, Rhode Island. He has practiced in the Longmont community since 2006. He lives in Longmont with his wife and three children and is honored to continue to serve the Longmont community. Dr. Barnett has over 15 years of experience in medical oncology and hematology and has particular interest in the areas of gastrointestinal and genitourinary malignancies. He is an advocate for cancer research, and actively participates in recruiting patients for clinical trials. He has received several awards recognizing his commitment to patient care including the Longmont Physician Service Excellence award. He currently serves on the partnership board for Rocky Mountain Cancer Centers. He actively collaborates with colleagues in a multidisciplinary approach to maximize patient outcomes from cancer treatment. He is known throughout the community as a very approachable and compassionate physician.
Provider Specialties
- Blood Cancers
- Gastrointestinal Cancers
- Anal Cancer
- Colorectal Cancer
- Esophageal Cancer
- Liver Cancer
- Pancreatic Cancer
- Stomach Cancer
- Genitourinary Cancers
- Adrenal Cancer
- Bladder Cancer
- Kidney Cancer
- Penile Cancer
- Prostate Cancer
- Testicular Cancer
Introduction Video
Care Philosophy
I believe in bringing my full attention and focus to each patient at every visit. I believe practicing medicine is an honor that gives us the opportunity to experience the wonderful humanity and resilience of our patients. I learn a great deal from my patients and getting to know each of them personally is the best part of my work.
Care Team
Lisa Tellier
View Profile

Locations
Reviews
Education
Fellowship
Medical Oncology & Hematology, Brown University School of Medicine, Providence, RI
Residency
Internal Medicine, Brown University School of Medicine, Providence, RI
Medical School
Southern Illinois University School of Medicine, Edwardsville, IL
Board Certifications
Hematology
Medical Oncology
Memberships
American Society of Clinical Oncology
Colorado Medical Society
Longmont United Hospital Cancer Committee, Chairman
Articles
Videos
Our providers accept all of the following insurances:
- Aetna
- Anthem BCBS Colorado
- Apostrophe Health
- Cigna
- Colorado Access
- First Health
- Humana Medicare Advantage
- *Kaiser (depending on market)
- Medicare
- Medicaid
- Multiplan/PHCS
- Optum Health / Optum Care CO
- PHPprime
- Rocky Mountain Health Plans
- TRICARE/HealthNET
- United Healthcare