ABSTRACT Background: L-Carnitine may protect cardiac muscle against oxidative stress, hypoxia and ischemia. The aim of this study was to assess the effect of L-Carnitine in improving systolic and diastolic function in patients with dilated cardiomyopathy. Methods: We studied 160 patients who were admitted to Critical Care Department, Zagazig University diagnosed as dilated cardiomyopathy. The patients were classified into 2 groups: Group I: Study Group: Includes 80 patients who received conventional anti failure measures plus L-Carnitine. L-Carnitine was given in a dose of 3gm/d divided in 3 doses, 1 gm at principal meals for up to 6 months. Group I subdivided into responders and non-responders. Group II: Placebo Group: Includes 80 patients who received conventional anti failure measures only. Serum carnitine and echocardiographic parameters as left ventricular ejection fraction (EF), global longitudinal strain (GLS) by speckle tracking echocardiography and E/E′ using tissue Doppler imaging, were measured before the start of therapy, at 2 and 6 months later. Results: Comparing the study versus placebo groups, there was statistically significant increase in EF in group I at 2 months (39.3±8% vs 33.52±4.8%, p: 0.001) and after 6 months (40.33±8% vs 34.5±4.8%, p: 0.001) as compared to group II respectively. Regarding GLS (- %), group I exhibited significant improvement in GLS at 2 months as compared to group II (16.5±2.9 vs 7.7±2.8, p: 0.001) which continued after 6 months (18.8±3.6vs 8.2±1.5, p: 0.001) respectively. Regarding E/E′ ratio, group I exhibited significant improvement in diastolic function at 2 and 6 months as compared to group II (p: 0.001) which continued after 6 months. There was no significant increase in levels of serum L carnitine in group I after 2 months (22.4±6.3 vs 19.4±2.5, p: 0.05) but there was significant increase in serum carnitine level after 6 months (35.8±10.1 vs 22.5±3.1, p: 0.01) as compared to group II. There was statistically positive significant correlation between EF and L-Carnitine (r= 0.6, p=0.001). Conclusion: As a metabolic supplement the early administration of L-Carnitine plus conventional anti failure measures to patients with cardiomyopathy provides a significant improvement as regards clinical signs of heart failure and echocardiographic parameters namely EF, GLS and E/E′ with consequent improvement in quality of life for these patients.