IMSC transplantation during CABG is considered one of the most promising methods to effectively deliver stem cells and has been widely studied in many trials. But the results of outcomes and safety of this modality still vary widely. We conducted this meta-analysis of randomized controlled trials (RCTs) to evaluate not only the outcome but also the safety of this promising method. A meta-analysis was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. A comprehensive literature search was undertaken using the PubMed, Scopus, and Cochrane databases. Articles were thoroughly evaluated and analyzed. Twenty publications about IMSC during CABG were included. Primary outcomes were measured using LVEF, LVESV, LVESVI, LVESD, LVEDV, LVEDVI, LVEDD, WMSI, and 6-MWT. Safety measures were depicted by total deaths, MACE, CRD, CVA, myocardial infarction, ventricular arrhythmia, and cardiac-related readmission. IMSC transplantation during CABG significantly improved LVEF (MD = 3.89%; 95% CI = 1.31% to 6.46%;p= 0.003) and WMSI (MD = 0.28; 95% CI = 0.01–0.56;p= 0.04). Most of the other outcomes showed favorable results for the IMSC group but were not statistically significant. The safety analysis also showed no significant risk difference for IMSC transplantation compared to CABG alone. IMSC during CABG can safely improve cardiac function and tend to improve cardiac volumes and dimensions. The analysis and application of influencing factors that increase patients’ responses to IMSC transplantation are important to achieve long-term improvement.