Background: Exercise may effectively reduce side effects caused by chemotherapy. However, no meta-analyses of exercise during or postchemotherapy for cancer patients have been definitely performed to guide clinical practice. Aims: To evaluate and summarize available scientific evidence to provide recommendations of an exercise intervention for cancer patients undergo chemotherapy. Methods: A systematic review and meta-analysis were performed with databases searching of MEDLINE, Cochrane Library, and Embase from their inception to October 15, 2017. Literature was selected to identify randomized controlled trials of exercise during or postchemotherapy for cancer patients. Risk-of-bias assessment was performed by two reviewers independently. Data were analyzed using the Cochrane Collaboration's RevMan 5.3 (Review Man, Copenhagen, Denmark). Results: A total of 10 trials with 838 participants were included in our study. Exercise could have a beneficial effect in cancer patients undergo chemotherapy in the outcome of physical fitness (MD: 0.16, 95% CI: 0.08-0.25, p < .01 and MD: 2.46, 95% CI: 1.44-3.47, p < .01) and depression (MD: -1.36, 95% CI: -2.68 to -0.04, p = .04), but not in FACT-G, FACT-B, anxiety, weight, and BMI (all p > .05). Exercise sequence (during or postchemotherapy) did not influence the effect of exercise for cancer patients undergo chemotherapy. In total, six studies were assessed as an overall low risk of bias. Subgroup analyses and sensitivity analyses reached results similar to those of the meta-analyses, which reflected our results were reliable and robust. Linking evidence to action: Exercise seems to have a beneficial effect on physical fitness and depression, but not on quality of life, anxiety, weight, and BMI. More specific and detailed description of the implementation of exercise programs should be proposed in the future.