Continuous glucose monitoring (CGM) provides important information to aid in achieving glycemic targets in people with diabetes.We performed a meta-analysis of randomized controlled trials (RCTs) comparing CGM with usual care for parameters of glycemic control in both type 1 and type 2 diabetes.Many electronic databases were searched for articles published from inception until 30 June 2019.We selected RCTs that assessed both changes in HbA1c and time in target range (TIR), together with time below range (TBR), time above range (TAR), and glucose variability expressed as coefficient of variation (CV).Data were extracted from each trial by two investigators.All results were analyzed by a random effects model to calculate the weighted mean difference (WMD) with the 95% CI. We identified 15 RCTs, lasting 12-36 weeks and involving 2,461 patients. Compared with the usual care (overall data), CGM was associated with modest reduction in HbA1c (WMD -0.17%, 95% CI -0.29 to -0.06, I2 = 96.2%), increase in TIR (WMD 70.74 min, 95% CI 46.73-94.76, I2 = 66.3%), and lower TAR, TBR, and CV, with heterogeneity between studies. The increase in TIR was significant and robust independently of diabetes type, method of insulin delivery, and reason for CGM use. In preplanned subgroup analyses, real-time CGM led to the higher improvement in mean HbA1c (WMD -0.23%, 95% CI -0.36 to -0.10, P < 0.001), TIR (WMD 83.49 min, 95% CI 52.68-114.30, P < 0.001), and TAR, whereas both intermittently scanned CGM and sensor-augmented pump were associated with the greater decline in TBR.Heterogeneity was high for most of the study outcomes; all studies were sponsored by industry, had short duration, and used an open-label design.CGM improves glycemic control by expanding TIR and decreasing TBR, TAR, and glucose variability in both type 1 and type 2 diabetes.