Introduction: Ribociclib, a cyclin-dependent kinase 4/6 inhibitor, has improved survival in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER 2)-negative advanced breast cancer. Despite remarkable efficacy, potential cardiac toxicities remain a concern. We undertook a combined analysis of randomized controlled trials (RCT) to estimate the incidence of prolongation of corrected QT interval (QTcF) associated with ribociclib. Methods: We performed systematic search of Embase, MEDLINE, and meeting abstracts till September 30, 2018, to find all phase 3 RCTs comparing ribociclib with other agents or placebo in patients with advanced breast cancer and reporting QTc prolongation as adverse event. Mantel-Haenszel method was used to calculate the pooled risk ratio (RR) and absolute risk difference (RD) with 95% CI. Fixed effects model was applied. Heterogeneity was assessed using I2 statistic. Results: Three phase III studies with 2,062 participants were included. Randomization ratio was 1 to 1 in MONALEESA-2 and 7 studies and 2 to 1 in MONALEESA-3 study. I2 statistic was 0, suggesting homogeneity across studies. Prolongation of QTcF >60 msec from baseline was observed in 72 patients (61 had post-baseline QTcF >480 msec) in ribociclib arm, compared to 7 in control arm. Pooled RR for prolongation of QTcF was 7.956 (95%CI: 3.683–17.187; P<.001) and RD was 0.055 (95%CI: 0.040–0.070; P<.001). The risk of having a post-baseline QTcF >480 msec was significantly higher with ribociclib vs control (pooled RR, 4.002; 95%CI: 2.161–7.412; P<.001; and RD, 0.039; 95%CI: 0.024–0.055; P<.001). A total of 16 (1.38%) patients in the ribociclib arm had dose reduction, interruption, or discontinuation due to QTcF prolongation, as opposed to 3 (0.33%) in control arm. Pooled RR and RD were statistically significant at 4.204 (95%CI: 1.333–3.260; P=.014) and 0.012 (95%CI: 0.004–0.021; P=.006), respectively. Conclusion: Advanced breast cancer patients may have cardiac dysfunction due to prior cardiotoxic chemotherapies. In our meta-analysis, ribociclib was associated with significantly higher risk of QTc prolongation and the resultant dosing inconsistencies and discontinuation. Early detection of this potential adverse event and timely intervention are critical.