Twenty-four crossbred ram lambs (1/2 Finnish Landrace ×1/2 Rahmani) aged 3-4 months and averaged 22.25±0.93 kg live body weight were randomly divided into three treatments (8 lambs in each) according to their live body weight. The experimental period lasted 6 months from May to October 2015. Ram lambs were orally treated with 0 (control), 1 (T1) and 2 (T2) mg rocket oil (RO)/kg LBW. Growth performance, puberty and semen characteristics of ram lambs, some blood parameters and economic efficiency were estimated. The results showed that final LBW of ram lambs at puberty increased (P>0.05) in T2 and T1 as compared to control. Total weight gain increase (P>0.05) in T2 compared with control (18.22 vs.16.62 kg). Average daily gain was higher (P>0.05) in T2 than in T1 and control (161.2 vs. 125.6 and 112.3 g/d). Ram lambs of T2 expressed first ejaculate (puberty) 34.6 days earlier (P<0.05) than those in control. Scrotal circumference and testes volume increased (P<0.05) in T1 and T2 compared with in control. Semen quality (ejaculate volume, initial motility, live spermatozoa, sperm cell concentration and sperm output) was better (P<0.05) in T2 and T1 than in control. Serum total antioxidant capacity was higher (P>0.05) in T2 than in control and T1. Relative economic feed efficiency increased for T1 and T2 lambs (111 and 137%) compared with controls. It could be conclude that daily addition of 2 mg rocket oil (watercress oil)/kg live body weight of ram lambs could lead to earlier age at puberty, improvement in growth performance at puberty, higher reproductive ability and better economic feed efficiency of ram lambs.