Two hundred and eighty eight of Sudani ducklings (144 from both males and females), 4-wks-old were used, weighed and divided into six experimental groups (three replicates each) for both sexes to investigate the effect of ducklings sex and dietary L-carnitine (LC) addition(0, 150, 300, 450, 600 and 750 mg/kg diet) in a factorial design (2 × 6) on growth performance, carcass traits and quality and blood constituents as well as economic efficiency under Egyptian summer conditions. Results indicated that, live body weight (LBW), body weight gain (BWG), feed consumption (FC) and production index (PI) were significantly (P≤0.01) higher for male ducklings than female, also, feed conversion ratio (FCR) was significantly (P≤0.05) improved during the whole experimental period (4-16 wks of age). However, dietary LC addition resulted in a significant (P≤0.01) improvement in BWG, FCR and PI during the experimental period than the control group. Abdominal fat and breast and thigh yield (%) were significantly higher for female than male ducklings. Eviscerated carcass and total edible parts (%) were significantly (P≤0.01) improved by supplementing different LC levels to the diet, while abdominal fat was significantly (P≤0.01) decreased. Breast yield (%) was significantly (P≤0.05) higher by feeding 450 mg LC/kg diet, only than the control, however, thigh yield (%) was significantly(P≤0.01) improved by feeding different LC levels except of 300 mg/kg. Furthermore, muscles ether extract (EE) content was significantly higher in both breast and thigh of female's ducklings than males, while crude protein (CP) was significantly decreased for female thigh muscles. Addition different LC levels to the diet resulted in a significant improvement of CP content for both breast and thigh muscles, while EE content was significantly decreased for them. Serum total cholesterol was significantly increased for female than male ducklings, whereas, both serum triglycerides and total cholesterol constituents were significantly decreased by supplementing different LC levels to the diet than the control. Supplementing different LC levels to the diet resulted in a significant increase in lymphocytes (L) cells (%), while heterophils (H) cells (%) and H/L ratio were significantly (P≤0.01) decreased than the control group. Net return and economic efficiency were significantly lowered for female ducklings than male, however, they significantly improved for ducklings fed different LC diets than those fed the control diet. These results indicated that dietary L-carnitine additionwith150 or 300 mg/kg could be maximize and improve the growth performance and carcass traits and quality as well as economic efficiency of Sudani ducklings especially males during growth period (4-16 wks of age) under Egyptian summer conditions.