Objective: To investigate the effect of diet and/or exercise in overweight or obese pregnant women on the risk of preeclampsia (PE). Methods: We performed a systematic review and meta-analysis of randomized controlled trials examining the effect of diet and/or exercise interventions in overweight and obese pregnant women on the risk of PE and hypertensive disorders. We completed a literature search through PubMed, Embase, Cinahl, Web of science, Cochrane CENTRAL Library from their earliest entries to November 2017 and from references of other systematic reviews. No language restrictions were applied. Relative risks (RR) with random effect were calculated with their 95% confidence intervals (CI). Results: There were 23 eligible trials (7236 participants), including 11 (5023 participants) investigating the effect of diet and three (387 participants) investigating the effect of exercise on risk of PE, 14 (4345 participants) investigating the effect of diet, five (884 participants) investigating the effect of exercise and one (304 participants) investigating the effect of diet and exercise on risk of hypertensive disorders. Most studies were considered to be at low risk of bias for random sequence allocation and incomplete outcome data but at high risk of bias for blinding of participant and personnel. The heterogeneity of the studies on PE was low (I2 = 0-11%), but the heterogeneity of the studies on hypertensive disorders was variable (I2 = 0-53%). In women randomized to diet and/or exercise, compared to expectant management, there was no significant difference in the risk of PE (RR 1.01, 95% CI 0.80-1.27; p = .96) or hypertensive disorders of pregnancy (RR 0.87, 95% CI 0.70-1.06; p = .17). In the intervention group, compared to expectant management, gestational weight gain was significantly lower (-1.47 kg, 95% CI -1.97 to -0.97; p < .00001). Metaregression weighted by the size of the studies showed no significant association between gestational weight gain and the risk of PE or hypertensive disorders (p = .314 and p = .124, respectively). Conclusions: Diet and exercise in overweight or obese pregnant women are beneficial in reducing gestational weight gain. However, these interventions do not reduce the risk of PE or hypertensive disorders of pregnancy. Keywords: Diet; RCT; exercise; meta-analysis; obese; preeclampsia.