The induction of in vivo reprogramming toward pluripotency has been demonstrated in several tissues utilizing either transgenic inducible mice or gene delivery approaches. However, the effects of exogenous reprogramming factor expression in the mammalian heart have not been previously reported. In the present study aimed to investigate the response of cardiac cells to ectopic Oct3/4, Sox2, Klf4, and cMyc (OSKM) expression in vivo using a non-integrating adenoviral vector. Direct intramyocardial injection of this vector achieved effective and transient OSKM overexpression in the healthy heart and after myocardial infarction. The expression of these factors induced transient upregulation of a number of endogenous pluripotency (endo-Oct3/4, Gdf3) and reprogramming related (Cdh1, Fut4) genes, confirming the induction of cell reprogramming. Despite the initiation of reprogramming, markers of fully de-differentiated cells including Nanog remained silenced, consistent with a partially reprogrammed state. Furthermore, no indications of tumorigenesis or teratoma formation were observed. Overall, these data suggest that adenoviral mediated OSKM delivery can be utilized to induce partial in vivo reprogramming. However, the absence of any clear regenerative effects after myocardial infarction indicates that further optimization of vector mediated reprogramming strategies is essential to overcome barriers to therapeutic efficacy.