Aim of this study was to investigate performance and puberty of ram lambs produced from pregnant ewes treated with different levels of arginine. This study was carried out at Sakha Animal Production Research Station, belonging to the Animal Production Research Institute in a cooperation with Animal Production Department, Faculty of Agriculture, Mansoura University. During November 2016, total of 45 Ossimi ewes (September mating season), 3-4 years of age and 39.59±0.15 kg live body weight (LBW ) were divided into three groups (15 head/each). Ewes in the 1^st group (G1) served as a control, ewes in the 2^nd (G2) and 3^rd (G3) groups were weekly treated with oral dose of 20 and 30 mg arginine (AR), respectively, for the duration of the treatment from the second month of pregnancy up to lambing. After lambing, total of 8 ram lambs produced from each group were taken and allotted in three groups similar to treatment of their dams. LBW of ram lambs was recorded at birth and monthly up to 12 month of age. In blood plasma of ram lambs, concentration of IgG and IgM at 2 days and 1, 3 and 4 wk of age, while concentration of total proteins, albumin,creatinine and glucose, and activity of aspartate (AST) and alanine (ALT) aminotransferase at 2, 4, 6 and 8 month of age were determined. Age and plasma testosterone concentration (PTC) of each ram lambs were determined at three pubertal stages, while semen of 1^st ejaculates (at puberty) was evaluated. Results showed that ram lamb LBW was higher (P<0.05) only in G3 than G1 at birth and at 5 to 12 month of age. Final ram lamb LBW at 12 month of age was higher by 10.2 and 15.9% in G2 and G3 than in G1, respectively. Plasma concentration of Immunoglobulin G (IgG) and Immunoglobulin M (IgM) after 2 days, 1, 3, and 4 wk of lambing was highest (P<0.05) in G3, followed by G2, while, G1 showed the lowest values. Plasma concentration of total proteins at 4 month of age and of albumin at 4 and 6 month of age increased (P<0.05), while glucose decreased (P<0.05) at 2 and 8 month of age in G2 and G3 as compared to those of G1. Creatinine increased (P<0.05) only in G3 as compared to G2 and G1 at 6 and 8 month of age, while activity of AST and ALT was not affected at all ages. At puberty, age of ram lambs was earlier (P<0.05) by 51.4 and 33.0 days and PTC was higher (P<0.05) by 22.5 and 18.8% in G2 and G3 than in G1. Ram lambs in G3 showed the best (P<0.05) semen characteristics of the 1^st ejaculation (volume, sperm motility and live sperm output / ejaculate), followed by G2. PTC was higher (P<0.05) in G2 and G3 than in G1 at 6 and 8 month of age, showing significantly (P<0.05) an opposite trend at 7 month of age, while insignificantly different at 5, 9 and 10 month of age. In conclusion, ram lambs of ewes treated with weekly oral dose of L-arginine-HCL (30 mg / ewe) from the second month of pregnancy up to lambing achieved early age and higher weight at puberty.