Understanding how human cardiomyocytes mature is crucial to realizing stem cell-based heart regeneration, modeling adult heart diseases, and facilitating drug discovery. However, it is not feasible to analyze human samples for maturation due to inaccessibility to samples while cardiomyocytes mature during fetal development and childhood, as well as dif?culty in avoiding variations among individuals. Using model animals such as mice can be a useful strategy; nonetheless, it is not well-understood whether and to what degree gene expression pro?les during maturation are shared between humans and mice. Therefore, we performed a comparative gene expression analysis of mice and human samples. First, we examined two distinct mice microarray platforms for shared gene expression pro?les, aiming to increase reliability of the analysis. We identi?ed a set of genes displaying progressive changes during maturation based on principal component analysis. Second, we demonstrated that the genes identi?ed had a differential expression pattern between adult and earlier stages(e.g., fetus) common in mice and humans. Our ?ndings provide a foundation for further genetic studies of cardiomyocyte maturation. Understanding how human cardiomyocytes mature is crucial to realizing stem cell-based heart regeneration, modeling adult heart diseases, and facilitating drug discovery. However, it is not feasible to analyze human samples for maturation due to inaccessibility to samples while cardiomyocytes mature during fetal development and used model animals such as mice can be a useful strategy; nonetheless, it is not well-understood whether and to what degree gene expression pro? les during maturation are shared between humans and mice. Thus, we performed a comparative gene expression analysis of mice and human samples. First, we examined two distinct mice microarray platforms for shared gene expression pro? les, aiming to increase reliability of the analysis. We identi? ed a set of genes displaying progressive changes during maturation based on principal component analysis. Second, we demonstrated that the genes identi? ed had a differential expression pattern between adult and earlier stages (eg., fetus) common in mice and humans. Our? ndings provide a foundation for further genetic studies of cardiomyocyte maturation.