Cultured primary cardiomyocytes have universally been used in the study of cardiovascular researches. Here, we offer an optimized protocol for isolation and identification of neonatal mouse cardiomyocytes. The main advantage of this technique over other methods is the high yield, steady cell viability and reproducibility. We can obtain 1×106 cardiomyocytes from 2-3 neonatal mice based on this method. Over the 90% isolated cells are cardiomyocytes, and cardiac fibroblasts and cardiac endothelial cells were removed as much as possible. In addition, we use only commercially available solutions and classical digestion enzymes, which is less-costly.