The experiment was carried out to evaluate the effect of common vetch seed (CVS), used at various levels (0, 15 and 25%), as a protein source in diets replacing different proportion of barley, wheat bran and soybean meal on fattening performance, carcass and meat quality characteristics of Awassi male lambs at approximately 8 months of age. The lambs were divided into three treatment groups, T1 (control, fed a diet without CVS; n = 12), T2 (15% CVS; n = 12) and T3 (25% CVS; n = 12), at the beginning of the fattening period. The T2 and T3 lambs were fed with a concentrate including 15 and 25% of ground CVS. The main protein source was soybean meal in T1 diet treatment, partially replaced by vetch in T2 and T3 diet treatments. All groups were fed a diet consisting of concentrate mixture offered ad libitum, and 300 g of grass hay per lamb per day during the 60 day fattening period. Daily feed intake, daily weight gain and feed conversion efficiency (concentrate and hay consumption for 1 kg of live weight gain) were 1.716 kg, 0.26 kg and 6.60 for T1, 1.756 kg, 0.28 kg and 6.27 for T2 and 1.806 kg, 0.29 kg and 6.23 for T3, respectively. Growth, carcass and meat quality traits were almost the same across the groups. In conclusion, CVS supplementation to diets of Awassi lambs at a 0, 15 and 25% rates showed no statistical differences in fattening performance, wholesale cuts of carcasses, meat color parameters (L* = lightness, a* = redness, b* = yellowness, H = huge angle and C = chroma) and pH values, but there were numerical differences (improvement) in feed conversion efficiency. © 2005 Society of Chemical Industry.