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Abstract Mitochondrial dysfunction is considered to be a key contributor to the development of heart failure. Replacing injured mitochondria with healthy mitochondria to restore mitochondrial bioenergy in myocardium holds great promise for cardioprotection after infarction. This study aimed to investigate whether direct transplantation of exogenous mitochondria derived from mesenchymal stem cells (MSC‐mt) is beneficial and superior in protecting cardiac function in a mouse model of myocardial infarction (MI) compared to mitochondria derived from skin fibroblast (FB‐mt) and to explore the underlying mechanisms from their effects on the endothelial cells. The isolated MSC‐mt presented intact mitochondrial morphology and activity, as determined by electron microscopy, JC‐1 mitochondrial membrane potential assay, and seahorse assay. Direct injection of MSC‐mt into the peri‐infarct region in a mouse MI model enhanced blood vessel density, inhibited cardiac remodeling and apoptosis, thus improving heart function compared with FB‐mt group. The injected MSC‐mt can be tracked in the endothelial cells. In vitro, the fluorescence signal of MSC‐mt can be detected in human umbilical vein endothelial cells (HUVECs) by confocal microscopy and flow cytometry after coculture. Compared to FB‐mt, MSC‐mt more effectively protected the HUVECs from oxidative stress‐induced apoptosis and reduced mitochondrial production of reactive oxygen species. MSC‐mt presented superior capacity in inducing tube formation, enhancing SCF secretion, ATP content and cell proliferation in HUVECs compared to FB‐mt. Mechanistically, MSC‐mt administration alleviated oxidative stress‐induced endothelial senescence via activation of ERK pathway. These findings suggest that using MSCs as sources of mitochondria is feasible and that proangiogenesis could be the mechanism by which MSC‐mt transplantation attenuates MI. MSC‐mt transplantation might serve as a new therapeutic strategy for treating MI.