Physical activity may have benefits for children undergoing intense treatment for cancer, but such programmes are challenging to implement. This systematic review aimed to investigate the feasibly of physical activity interventions during intense cancer treatment for children and adolescents.A systematic search of seven electronic databases (Cumulative Index to Nursing and Allied Health Literature, Medical Literature Analysis and Retrieval System Online, Public/Publisher MEDLINE, Psychological Information Database, Sportsdiscuss, Excerpta Medica Database, Allied and Complementary Medicine Database) from 2005 to August 2015 was completed. The risk of bias was assessed using the Downs and Black Checklist and The Critical Review Form-Qualitative Studies. Results were summarised descriptively across eight domains of feasibility: acceptability, demand, implementation, adaptation, practicality, integration, expansion and limited efficiency testing (including effectiveness).Eleven quantitative studies and one qualitative study were identified for inclusion. Physical activity interventions were typically supervised, individualised programmes that prescribed a variety of activity types for hospital inpatients. There was evidence that physical activity interventions during the intense phase of cancer treatment were acceptable to parents and children, safe and successfully implemented. A trend of positive effects across all aspects of functioning was noted. Data were unavailable documenting feasibility for the domains of integration, adaptation and expansion.There is preliminary evidence that physical activity interventions are feasible, in that they are acceptable, safe and potentially beneficial for children with cancer but more work needs to be done to understand the most effective ways to implement these types of programmes.