This study was conducted to evaluate the effects of weaning age (early, traditional and late weaning), parity number (first, second and third or more), birth type (single and twins) and sex of lamb (male and female) on growth performance of Ossimi lambs during post-weaning period. One hundred and five Ossimi lambs distributed into 3 groups based on their weaning age. Lambs of early weaning group weaned at 56 days age, while, the second and third groups of lambs were remained with their mothers until 84 days (for traditional) and 112 days (for late weaning). The study performed at the experimental farm belongs to Faculty of Agriculture at Moshtohor, Benha University, Egypt, and lasted 240 days. Monthly live body weight (LBW) was recorded individually, while average daily gain (ADG) and total weight gain (TWG) were calculated as growth indices. Both total and daily feed intake (TFI and DFI) of dry matter were determined, then feed conversion ratio (FCR) and economical feed efficiency (EFE) were calculated. Regarding the effect of weaning age, results indicated that early weaned lambs showed a significant (P