Introduction: The purpose of this study was to determine the effects of L-carnitine supplementation on carbohydrate (CHO) and fat metabolism after resistance exercise. Materials and Methods: In this investigation, using a double blind, randomized, crossover, repeated measure design (1 wk washout), 10 healthy resistance-trained men (Mean±SD: age, 24.03±2.00 yr mass, 72.26±5.31 kg height, 173.90±5.02 cm) consumed 2 g placebo or LC supplement daily for one week and then performed 6 exercises of a resistance exercise protocol. Each workout was performed for 3 sets of 12 repetitions with 55% 1RM and rest periods were kept to 60 s between all sets and workout. Expired gases were measured for calculating CHO and fat oxidation. Venous blood samples were obtained before and after supplementation, immediately after resistance exercise and after the 1^st and 24^th hour after resistance exercise. Samples were analyzed for markers of glucose, NEFA, glycerol and insulin. Also L-carnitine plasma concentrations were measured, before and after supplementation. Results: The results of this study suggest that plasma carnitine concentrations increased 14% (p≤0.05) with L-carnitine supplementation, with no change in the placebo trial. Compared to the placebo trial, CHO oxidation was reduced significantly (p≤0.05) with L-carnitine supplementation immediately after resistance exercise. However there were no statistically significant differences between the L-carnitine and the placebo conditions for any of the other variables examined (p>0.05). Conclusions: Increased plasma insulin concentrations with L-carnitine and placebo after resistance exercise attenuated result in attenuate fat oxidation in this study.