Background: Gestational diabetes mellitus (GDM) is one of the most common complications of pregnancy and its prevalence worldwide is increasing along with enhancing type two of diabetes. Contrary results have been found in some review articles that examine the effect of exercise activities on preventing GDM, regardless of obesity. Therefore, the aim of this study was to systematically review the articles on the effect of exercise activities on the prevention of GDM in obese and overweight pregnant women. Main text: Literature was retrieved by formally searching PubMed, Embase, Cochrane library, Web of Science, Scopus, Proquest and by hand searching of reference lists of related articles. Finally, a total of eight literatures included, and Review manager 5.3 and STATA 14.0 statistical software were utilized for processing. In order to investigate the effect of sports activities on the incidence of GDM, the risk ratio (RR), and for quantitative indices, the standardized mean difference (SMD) with 95% confidence interval (CI) for each study was calculated. Out of 5107 papers identified, eight papers with 1441 participants included in meta-analysis (intervention group 727, control group 714). In the intervention group, 143 (19.66%, 95% CI 76.83 to 22.74) and in the control group, 196 (27.45%, 95% CI 20.24 to 30.88%), pregnant women had diabetes. The RR of gestational diabetes was 0.76 (95% CI 0.56 to 1.03, I2 = 50%, P = 0.05). In studies that the time for the intervention was three times a week or less, effect of intervention was significant in reducing the incidence of diabetes (RR: 0.59, 95% CI 0.46 to 0.76, I2 = 0%, P = 0.47). However, in studies with repeat of intervention was more than three times a week, the effect of intervention between two intervention and control groups was not different (RR: 1.03, 95% CI 0.78 to 1.35, I2 = 0%, P = 0.46). Conclusions: The exercise activities, alone, in obese or overweight pregnant women did not have a significant effect on the overall incidence of GDM, but considering the effect measure, the incidence of GDM was 24% lower in the intervention group than control group. This difference is considerable in the two groups. As the systematic review literatures both represent the information gap on the research subject and pave the way for further studies so it seems that there is a need for more randomized controlled trials so that we can make a complete conclusion on the type, intensity and duration of exercise in preventing GDM.