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Theresa Mortensen, MSN,  NP

Theresa Mortensen, MSN, NP

(707) 763-0600
Primary Specialties
  • Oncology - Medical
Medical Groups & Affiliations
  • St. Joseph Health Medical Group
  • Additional Languages Spoken

Primary Office

Medical and Radiation Oncology - Petaluma
110 Lynch Creek Way
Suite A
Petaluma, CA 94954
(707) 763-0600
(707) 765-1757
Mon - Fri
Web Page:

Secondary Office

Medical and Radiation Oncology - Santa Rosa
3555 Round Barn Circle
Santa Rosa, CA 95403
(707) 528-1050
(707) 525-3874

Physician Bio

Theresa has been providing quality care as a Nurse Practitioner to oncology/nematology patients in the in-patient and outpatient environment for more than 30 years.

She implemented the hereditary cancer syndrome program, which provides assessment and counseling services for high-risk individuals and their family members. Prior to her tenure as a NP, Theresa attended patients as staff nurse for Redwood Regional Medical Group from 1996 to 2002 and is now part of St. Joseph Health Medical Group, providing clinical expertise and training with the majority of her focus on solid tumors (example breast, lung, colon etc), as well as lymphomas, CML, MDS, and CLL. She is also specialty trained to perform bone marrow biopsies.

Teresa loves to educate patients, families, and colleagues - when she is not seeing them in clinic, she gives educational talks on cancer genetics, metastatic colon cancer, CML, MDS, and breast cancer. Theresa is an extremly caring Nurse Practitioner and takes pride in caring for the oncology patient and their family in the outpatient setting, including the administration of chemotherapeutic agents and support measures as needed.


Theresa is a member of APSHO which is an advanced practice oncology group and Sigma Theta Tau which is an honor society through SSU.