Purpose: We determined the barriers to and facilitators of exercise promotion by health care professionals (HCPs) for women with breast cancer (BC). Methods: The study was a qualitative descriptive study. Semi-structured interviews were conducted with HCPs who treat individuals with BC in Ontario. The interviews were recorded and transcribed. Two reviewers independently used content analysis to determine codes and themes developed in the interviews. NVivo 10 was used during the coding process. Results: A total of 24 HCPs participated in this study. The data from the interviews were grouped into five main categories: (1) institutional barriers, (2) HCP barriers, (3) perceived patient barriers, (4) facilitators (resource and service needs), and (5) patient characteristics. A graphic depiction of the interaction was created for these categories and how they affect the promotion of exercise for women with BC. Conclusions: Participants in this study identified several barriers to exercise promotion at the institutional, professional, and patient levels and suggested several strategies to facilitate exercise promotion. These findings can inform future exercise interventions to increase exercise adherence and engagement in this population.