Objective To evaluate the effect of aerobic exercise on cognitive function in people with mild cognitive impairment (MCI). Design Systematic review and meta-analysis of aerobic exercise intervention for cognitive function in older adults with MCI. Data sources PubMed, EMBASE, SinoMed, China National Knowledge Infrastructure (CNKI), Wanfang and Chinese Science and Technology Periodical (VIP) databases from their inception to 31 January 2015, the Cochrane Central Register of Controlled Trials (Cochrane Library, 2015, Issue 3) and the reference lists of all retrieved articles. Eligibility criteria Randomised controlled trials, older adults with MCI, aerobic exercises compared with no specific exercise intervention for global cognitive ability and any specific domains of cognition. Data synthesis Meta-analysis was conducted with RevMan V.5.3 software using the fixed-effect model for the available data without significant heterogeneity, or the random-effect model was used if appropriate. Results 11 studies were identified involving 1497 participants. Meta-analysis showed that aerobic exercise significantly improved global cognitive ability (Mini-Mental State Examination (MMSE) scores: MD=0.98, 95% CI 0.5 to 1.45, p<0.0001; Montreal Cognitive Assessment (MoCA) scores: MD=2.7, 95% CI 1.11 to 4.29, p=0.0009); weakly, positively improve memory (immediately recall: SMD=0.29, 95% CI 0.13 to 0.46, p=0.0005; delay recall: SMD=0.22, 95% CI 0.09 to 0.34, p=0.0005). No significant improvement was found in other domains of cognition. Conclusions Aerobic exercise led to an improvement in global cognitive ability and had a positive effect with a small effect size on memory in people with MCI. However, owing to the limitations of the included studies, these findings should be interpreted cautiously.