Introduction: Physical activity is beneficial for the physical and psychological health of patients with prostate cancer (PCa). Health-care practitioners are ideally positioned to promote physical activity to their patients. Aim: To identify factors that influenced health care practitioners to either promote or not promote physical activity to their patients with PCa. Methods: Individual interviews were conducted with 16 Auckland-based health-care practitioners, including specialists (oncologists and urologists), physiotherapists and complementary and alternative (acupuncturists) health-care practitioners. Data were analysed using an inductive thematic approach. Results: Treatment-related factors (ie counteracting side-effects of hormone suppression treatment), longer life expectancy and risk factors for other conditions appeared to influence the promotion of physical activity to patients. Time constraints of consultations and complex medical issues were barriers to the promotion of physical activity. Conclusions: This study found that a variety of health-care practitioners are providing some degree of physical activity advice to their patients with PCa. Collaborative practice among health-care practitioners to verbally reinforce the benefits of physical activity, coupled with referral to experts in physical activity promotion/rehabilitation (such as physiotherapists), should be encouraged for best practice care.