PURPOSE: Reviews of yoga research that distinguish results of trials conducted during (versus after) cancer treatment are needed to guide future research and clinical practice. We therefore conducted a review of non-randomized studies and randomized controlled trials of yoga interventions for children and adults undergoing treatment for any cancer type. METHODS: Studies were identified via research databases and reference lists. Inclusion criteria were the following: (1) children or adults undergoing cancer treatment, (2) intervention stated as yoga or component of yoga, and (3) publication in English in peer-reviewed journals through October 2015. Exclusion criteria were the following: (1) samples receiving hormone therapy only, (2) interventions involving meditation only, and (3) yoga delivered within broader cancer recovery or mindfulness-based stress reduction programs. RESULTS: Results of non-randomized (adult n = 8, pediatric n = 4) and randomized controlled trials (adult n = 13, pediatric n = 0) conducted during cancer treatment are summarized separately by age group. Findings most consistently support improvement in psychological outcomes (e.g., depression, distress, anxiety). Several studies also found that yoga enhanced quality of life, though further investigation is needed to clarify domain-specific efficacy (e.g., physical, social, cancer-specific). Regarding physical and biomedical outcomes, evidence increasingly suggests that yoga ameliorates sleep and fatigue; additional research is needed to advance preliminary findings for other treatment sequelae and stress/immunity biomarkers. CONCLUSIONS: Among adults undergoing cancer treatment, evidence supports recommending yoga for improving psychological outcomes, with potential for also improving physical symptoms. Evidence is insufficient to evaluate the efficacy of yoga in pediatric oncology. We describe suggestions for strengthening yoga research methodology to inform clinical practice guidelines.