OBJECTIVES: The objective of this meta-analysis is to systematically review the evidence on effects of exercise interventions in comparison to usual care with respect to physical fitness, fatigue, quality of life, anxiety and depression in hematopoietic stem cell transplantation patients for a hematological malignancies. And we are more focused on the optimal opportunity to exercise in hematopoietic stem cell transplantation recipients. METHOD: Databases were searched up to June 2018. We included randomized controlled trials comparing exercise with usual care in adult patients who had a hematologic malignancy. Standard mean differences were calculated and pooled to generate summary effect sizes and 95% confidence intervals. The Cochrane Collaboration Risk of Bias Tool was used to assess the methodological quality of the studies. RESULTS: This meta-analysis showed that exercise had a positive effect on lower muscle strength, fatigue and quality of life and had no effects on patients' cardiorespiratory fitness, upper muscle strength, psychosocial fitness and adverse events. Subgroup analysis showed that exercise had a favorable effect on upper/lower muscle strength, fatigue and quality of life when starting exercise pre-transplant, but exercise had no effects, except on quality of life when starting exercise after transplant. And patients in the pre-transplant exercise group did not exercise more graft vs host disease events nor deaths. CONCLUSION: Therefore, we can conclude that the optimal timing for the hematopoietic stem cell transplantation recipients to begin exercise training is before transplantation.