The efficacy of post-percutaneous coronary intervention (PCI) intracoronary injection with bone marrow mesenchymal stem cells (BMSCs) in patients with acute myocardial infarction (AMI) remains controversial. Here, 58 patients with AMI undergoing PCI were randomly divided into two groups: BMSC and control groups. Autologous BSMCs were then generated in vitro from the BMSC patients. After transplantation, left ventricular ejection fraction (LVEF), left ventricular end-diastolic dimensions (LVDd), and infarct size (IS) were evaluated in both groups. LVEF, LVDd, and IS improved after BMSC transplantation but the changes were not significantly different from those in the controls. The number of adverse events and rehospitalization rates after 1 month were significantly higher in the control group than in the BMSC group. BMSC transplantation thus benefits patients by decreasing the number of adverse events and reducing the rehospitalization rate in the early stages following PCI.