We compared the functional outcome of Isl-1⁺ cardiac progenitors, CD90⁺ bone marrow-derived progenitor cells, and the combination of the two in a rat myocardial infarction (MI) model. Isl-1⁺ cells were isolated from embryonic day 12.5 (E12.5) rat hearts and expanded in vitro. Thy-1⁺/CD90⁺ cells were isolated from the bone marrow of adult Sprague-Dawley rats by immunomagnetic cell sorting. Six-week-old female Sprague-Dawley rats underwent permanent left anterior descending (LAD) coronary artery ligation and received intramyocardial injection of either saline, Isl-1⁺ cells, CD90⁺ cells, or a combination of Isl-1⁺ and CD90⁺ cells, at the time of infarction. Cells were delivered transepicardially to the peri-infarct zone. Left ventricular function was assessed by transthoracic echocardiography at 1- and 4-week post-MI and by Millar catheterization (-dP/dt and +dP/dt) at 4-week post-MI. Fluorescence in situ hybridization (Isl-1⁺cells) and monochrystalline iron oxide nanoparticles labeling (MION; CD90⁺ cells) were performed to assess biodistribution of transplanted cells. Only the combination of cells demonstrated a significant improvement of cardiac function as assessed by anterior wall contractility, dP/dt (max), and dP/dt (min), compared to Isl-1⁺ or CD90⁺ cell monotherapies. In the combination cell group, viable cells were detected at week 4 when anterior wall motion was completely restored. In conclusion, the combination of Isl-1⁺ cardiac progenitors and adult bone marrow-derived CD90⁺ cells shows prolonged and robust myocardial tissue repair and provides support for the use of complementary cell populations to enhance myocardial repair.