The α₂-isoform of the Na,K-ATPase (α₂) is the minor isoform of the Na,K-ATPase expressed in the cardiovascular system and is thought to play a critical role in the regulation of cardiovascular hemodynamics. However, the organ system/cell type expressing α₂ that is required for this regulation has not been fully defined. The present study uses a heart-specific knockout of α₂ to further define the tissue-specific role of α₂ in the regulation of cardiovascular hemodynamics. To accomplish this, we developed a mouse model using the Cre/loxP system to generate a tissue-specific knockout of α₂ in the heart using β-myosin heavy chain Cre. We have achieved a 90% knockout of α₂ expression in the heart of the knockout mice. Interestingly, the heart-specific knockout mice exhibit normal basal cardiac function and systolic blood pressure, and in addition, these mice develop ACTH-induced hypertension in response to ACTH treatment similar to control mice. Surprisingly, the heart-specific knockout mice display delayed onset of cardiac dysfunction compared with control mice in response to pressure overload induced by transverse aortic constriction; however, the heart-specific knockout mice deteriorated to control levels by 9 wk post-transverse aortic constriction. These results suggest that heart expression of α₂ does not play a role in the regulation of basal cardiovascular function or blood pressure; however, heart expression of α₂ plays a role in the hypertrophic response to pressure overload. This study further emphasizes that the tissue localization of α₂ determines its unique roles in the regulation of cardiovascular function.