Chick performance, carcass traits and some blood biochemical parameters of broilers fed basal diet supplemented with L-carnitine or silymarin were studied for 42 days in the experiment. This study was conducted on 300 chicks (Ross 308 hybrid) divided randomly into three groups, (100 chicks per each) and each group was subdivided into four replicates (25 chicks for each). Chicks in the first group (C) were fed ad-libitum on the basal control diets (starter from 1 to 21 days of age, and grower- finisher from 22 to 42 days of age) without addition of L-carnitine and silymarin. Birds in the second group (L) received the same basal diet supplemented with L-carnitine (300mg/kg diet) while, chicks in the third group (S) fed on basal diet supplemented with silymarin (160mg/kg diet) during two experimental periods. The results showed that, supplementation of silymarin and L-carnitine improved significantly body weight gain at starting period. The highest body weight gain was recorded with silymarin supplemented group (662±20 g) in comparison with control (593.5±20g). At the end of the experiment (42 days), the best cumulative weight gain and feed conversion recorded in silymarin supplemented group (2163±23g & 1.9) followed by L-carnitine supplemented group (2103.5±16g &1.94) while the birds fed on control diet had the worst values (1893.8±65g & 1.96). Abdominal fat deposition of L and S groups were significantly lower than control group, while no significant differences were observed in dressed carcass and breast muscle weights. From the results of this study, it can be concluded that, the addition of silymarin to broiler diets significantly improved the body weight gain and feed conversion indices all over the period of raising, while L-carnitine improved growth performance of broilers at growing-finishing period (high energy diet). Finally, it is recommended that we can use both silymarin and L-carnitine as feed additives at growing-finishing period.