Transplantation of mesenchymal stem cells (MSCs) has emerged as a potential treatment for ischemic heart repair. Previous studies have suggested that Wnt11 plays a critical role in cardiac specification and morphogenesis. In this study, we examined whether transduction of Wnt11 directly increases MSC differentiation into cardiac phenotypes. MSCs harvested from rat bone marrow were transduced with both Wnt11 and green fluorescent protein (GFP) (MSC^Wnt11) using the murine stem cell virus (pMSCV) retroviral expression system; control cells were only GFP-transfected (MSC^Null). Compared with control cells, MSC^Wnt11 was shown to have higher expression of Wnt11 by immunofluorescence, real-time polymerase chain reaction, and western blotting. MSC^Wnt11 shows a higher expression of cardiac-specific genes, including GATA-4, brain natriuretic peptide (BNP), islet-1, and α-actinin, after being cultured with cardiomyocytes (CMs) isolated from ventricles of neonatal (1–3 day) SD rats. Some MSC^Wnt11 were positive for α-actinin when MSCs were cocultured with native CMs for 7 days. Electron microscopy further confirmed the appearance of sarcomeres in MSC^Wnt11. Connexin 43 was found between GFP-positive MSCs and neonatal rat CMs labeled with red fluorescent probe PKH26. The transdifferentiation rate was significantly higher in MSC^Wnt11 than in MSC^Null, as assessed by flow cytometery. Functional studies indicated that the differentiation of MSC^Wnt11 was diminished by knockdown of GATA-4 with GATA-4-siRNA. Transduction of Wnt11 into MSCs increases their differentiation into CMs by upregulating GATA-4.