Adipose-derived stem cell (ADSC) transplantation has been proposed to improve cardiac function and acute myocardial infarction (AMI). Recently, cell sheet technology has been investigated for its potential applicability in cardiac injury. However, a detailed comparison of the functional recovery in the injured myocardium between cell sheets and conventional cell injection has not been adequately examined. ADSCs were isolated from the inguinal fat tissue of ICR mice. Three groups of AMI induction only (sham), intramyocardial injection of ADSCs (imADSC), and ADSC sheet transplantation (shADSC) were compared by using rat AMI models. Engraftment of ADSCs was better sustained through 28 days in the shADSC group compared with the imADSC group. Ejection fraction was improved in both imADSC and shADSC groups compared with the sham group. Ventricular wall thickness in the infarct zone was higher in the shADSC group compared with both imADSC and sham groups. Growth factor and cytokine expression in the implanted heart tissue were higher in the shADSC group compared with both imADSC and sham groups. Furthermore, only the shADSC group showed donor-derived vessels at the peri-infarct zone. Taken together, these results indicate that, although shADSC resulted in a similar improvement in left ventricular systolic function, it significantly promoted cellular engraftment and upregulated growth factor and cytokine expression, and, ultimately, attenuated adverse cardiac remodeling in rat AMI models compared with imADSC.