Human cartilage is reported to contain multipotent stromal cells. We evaluated the effect of human cartilage-derived stromal cells (CDSCs) on heart function when transplanted into the infarcted myocardium of rats. CDSCs were isolated and cultured from human articular cartilage and subjected to fluorescence-activated cell sorting (FACS) analysis. The CDSCs were consistently negative for CD14, CD34, CD38, CD45, CD49f, CD104, CD105, CD106, CD117, HLA-DR, and ABCG-2, and positive for CD10, CD44, CD71, CD73, CD90, CD147, and HLA-A, -B, and -C by FACS analysis. Myocardial infarction (MI) was created in rats by ligation of the left anterior descending artery. Three weeks after MI, the CDSCs labeled with Hoechst stain were injected into the infarct and border zone. Echocardiography, histological examination, and reverse transcription-polymerase chain reaction (RT-PCR) were performed 4 weeks after cell transplantation. Echocardiography indicated that CDSC transplantation could improve heart function. The number of capillaries increased in the injection regions in the transplantation group. Histological examination showed that Hoechst-labeled CDSCs in islands within the infarcted region were stained positively for desmin and smooth muscle actin but negatively for alpha-sarcomeric actin and troponin-I. RT-PCR results indicated the expression level of collagen I, collagen III, tissue inhibitor of metalloproteinase-1, transforming growth factor-beta1, and vascular endothelia growth factor were much higher in the scar tissue in the transplantation group than in the medium and control groups. Our findings suggested that CDSCs might promote angiogenesis, prevent left ventricular remodeling, and improve the heart function when transplanted into injured heart in the rat model of myocardial infarction.