Our aim was to synthesise the existing empirical literature and theoretical perspectives on the physical activity (PA) promotion practices and determinants of cancer clinicians and health professionals. We conducted a narrative review of theory and evidence to develop practice recommendations for improving the promotion of PA to cancer patients. Surveyed health professionals were aware of many benefits of PA for their cancer patients, although only ~40 % promoted PA to selected cancer patients. Walking was the most commonly promoted form of PA, with this promoted to assist patients control their weight and cardiovascular health risk. Barriers to promotion of PA included lack of time and knowledge of PA and behaviour change skills. Health professionals appear interested in promoting PA to their cancer patients, yet encounter several barriers. Further research is warranted to assist health professionals improve their PA promotion. An adapted reflective-impulsive model of social behaviour shows promise for assisting health professionals overcome barriers and provides an evidence-based theoretical framework for improving communication with patients. Universities, hospitals and/or health-care accreditation organisations also have important roles to play in assisting health professionals improve their promotion of PA to patients.