Carnitine is a vital biologic substance for transporting fatty acids into myocytes and facilitates fatty acids β-oxidation for energy production. There are not enough reports about its anti-apoptotic effects during ischemia/reperfusion. In this study, effects of L-Carnitine on apoptosis in the ischemic isolated rat hearts were investigated. Male Sprague-Dawley rats (270-330g) were divided into 4 groups randomly and were anesthetized by sodium pentobarbital (50-60 mg/kg-ip). Heart was removed and quickly mounted on a Langendorff apparatus and perfused by a modified Krebs-Henseleit solution under constant pressure at 37 °C. In control group (n=6), the hearts were perfused only by normal Krebs -Henseleit solution at stabilization, 30 min regional ischemia and 120 min reperfusion, while in the test groups (1-3 groups, n=6 in each group), during ischemia / reperfusion, the hearts were perfused with 0.5,2.5 and 5mM of L-Carnitine - enriched Krebs-Henseleit solution, respectively. At the end of reperfusion, Immunohistochemical detection of apoptotic cells was performed by using an in situ apoptosis detection kit. The number of TUNEL-positive cardiomyocytes was counted in five random high-power fields in each sample. Data represented as mean ± sem for each group. In control group, the number of apoptotic cells were 48 ±3 while in the test groups, addition of L-Carnitine (0.5, 2.5 and 5mM) into the Krebs solution during ischemia and reperfusion, reduced the number of apoptotic cells to 6±1, 4±1 and 3±1, respectively (p<0.001). There was no significant difference between and within test groups using ANOVA one-way. Considering these results, we conclude that L-carnitine has a protective effect against cardiac ischemic reperfusion injuries as a reduction of apoptotic cardiomyocytes.