Courtney A. O'Brien, DO
Accepting new patients

Courtney A. O'Brien, DO

  • Rheumatology
Average rating: 4.9
| 195 ratings
Simi Valley Primary & Specialty Care | 2655 1st Street, Suite 380, Simi Valley, CA 93065


Dr. Courtney O’Brien is a board certified rheumatologist who practices in Simi Valley and Porter Ranch. Her clinical interests include diagnostic musculoskeletal ultrasound, ultrasound guided injections,  systemic lupus erythematosus, vasculitis, rheumatoid arthritis and general rheumatology.

Dr. O’Brien received her medical degree from Nova Southeastern University of Osteopathic Medicine in Fort Lauderdale, Florida. As a D.O. trained physician, she received additional hands-on training in manipulative medicine with a focus on holistic care in treating the mind and body. She became fascinated with the field of rheumatology early in her career during medical school when she volunteered at a camp for children suffering from juvenile rheumatoid arthritis. She then returned to her hometown of Chicago to complete her internal medicine residency at Rush University Medical Center, during which time she published research under the mentoring of Dr. Meenakshi Jolly whose focus was on health-related qualify of life with lupus and cardiovascular risk awareness in rheumatoid arthritis.

The final step of her training led her to rheumatology fellowship at UCLA. She had the opportunity to work closely with Dr. Tanaz Kermani researching cases of overlapping rheumatoid arthritis and ANCA-associated vasculitis. Furthermore, she was accepted into the prestigious USSONAR program for musculoskeletal ultrasound training, led by one of the most nationally recognized musculoskeletal ultrasound experts, Dr. Eugene Kissin. In her practice, she regularly incorporates ultrasound into her diagnostic workup in order to provide the highest and most comprehensive quality of care. 

During her rheumatology fellowship training, she became familiarized with the vast, diverse population of Los Angeles by treating patients across several health systems including the county hospital Harbor-UCLA, the West Los Angeles VA Medical Center, and at the main academic hospitals of Santa Monica and Westwood UCLA.  Having resided in multiple urban cities, Dr. O’Brien is no stranger to the complexities and uniqueness of patients from different backgrounds.  She has also done extensive, international medical work throughout her undergraduate time at Penn State University in Global Medical Brigades, her medical school’s International Outreach Program and pursuing the Global Health Care Track in residency. She has traveled to various countries providing care to underserved populations including rural Haiti, Dominican Republic, Argentina, Brazil, and Honduras. In her free time, she is an avid outdoor enthusiast. She enjoys hiking, paddle boarding, roller skating, skiing, camping, and beach volleyball.




Medical Board Certifications

Rheumatology, American Board of Internal Medicine, 2022
Internal Medicine, American Board of Internal Medicine, 2020


Rheumatology, University of California, Los Angeles, 2022


Internal Medicine, Rush University, 2020


DO, Nova Southeastern University College Of Osteopathic Medicine, 2017

Hospital Affiliations

Ronald Reagan UCLA Medical Center

Medical Services


  • Aetna
  • Anthem Blue Cross
  • Blue Shield of California
  • Centivo
  • Cigna
  • First Health
  • Health Net of California
  • Interplan (part of HealthSmart)
  • L.A. Care
  • MultiPlan
  • UFCM Health System
  • Prime Health Services
  • Private Healthcare Systems (PHCS)
  • UnitedHealthcare

The list of health care plans above may not be comprehensive and could change. 
Please contact your benefits coordinator or health insurance company directly to verify coverage.

Visit our health insurance information page for more details.