Objective To examine women's experiences of enablers and constraints to physical activity participation after being diagnosed with breast cancer while mothers of dependent children. Methods In-depth, semi-structured interviews were conducted with 36 Australian women diagnosed with breast cancer while mothers of dependent children. Results Social, structural and individual enablers and constraints to women's participation in physical activity included level of intimate partner support, daily household and childcare responsibilities, post-treatment pain and fatigue and level of priority for and pleasure derived from physical activity participation. Conclusions The study concludes that social enablers and constraints, particularly partner support and gendered identity, were powerful in framing women's participation. Implications for those working in survivorship care include the need to consider ways to address women's gendered identities and their associated social roles, relationships and responsibilities when designing strategies to increase breast cancer survivors' physical activity participation. Further research is needed to understand the prevalence of the effects of perceived partner support on breast cancer survivors' physical activity participation.