Total of 75 mature healthy (1/2 Finnish Landrace × 1/2 Rahmani ewes) at 3-6 years of age and weighing approximately 45.21 kg were divided into three similar groups (control, G₂ and G₃). The first group was fed the control diet (G₁). While, fish oil was added to the control diet at level of 1.5 and 3% of total DM intake for G₂ and G₃, respectively (first trail).While, in the second trail, 24 female lambs at 3 months of age with an average live body weight of 14.5±0.6 kg were randomly divided into three groups (8 lambs each). The first group was fed a basal diet, while G₂ and G₃ treated with fish oil at 1.5 and 3% of total DM intake, respectively. The results of this study indicated that the live body weight of ewes was not affected significantly by dietary treatments during pregnancy period and after lambing. Percentage of ewes exhibited estrus was higher in G₂ (68%) than in G₁ and G₃ (44 and 48%, P<0.05), respectively. Fertility rate was 77.7, 70.5 and 100% in control, G₂ and G₃, (P<0.05). Litter size tended to gradually increase with increasing fish oil level. The results indicated that added fish oil (G₂ and G₃) led to increase total milk yield by about 45.2 % and 38.1 % than the control group but the differences were not significant. Age at puberty in ewe lambs was 318.1, 273 and 290.3 days for control, G₂ and G₃, respectively (P<0.05). Average daily gain of ewe lambs was the highest level (P<0.05) in G₃ (103.7 g) followed by G₂ (98.15 g), while G₁ had the lowest value (70.74 g). The lowest feed cost/kg gain was recorded in G₂ and G₃ (19.86 and 19.49 LE, respectively), while the highest feed cost/kg gain was recorded in G₁ (23.72 LE). On the light of the foregoing results, fish oil addition at rate of 1.5 and 3% to mature ewes and growing lambs had beneficial effects on productive and reproductive performance.