The aim of this study was to evaluate the effect of sex on fattening performance and carcass characteristics of Kivircik lambs. Fifty head weaned Kivircik lambs, half males and half females, were used in fattening period. After weaning, the growth and feed consumption of the male and the female lambs fattened for 56 days were recorded. Average daily weight gain differed significantly (P<0.01) between the males and the females (294.9 and 214.2 g, respectively). A total of 10 lambs (5 males and 5 females) were slaughtered and the left side of the carcasses was cut into five joints. Dressing percentage (hot/cold) based on full weight and empty body weight were lower (P<0.05) for the males than the female lambs. Sex had a significant effect on kidney-knob and channel fat weight, M. longissimus dorsi section area (MLDA) and liquid expelled (P<0.01). Sex primarily affected the quantity of all types of fat deposits. The male lambs had higher muscle, muscle/bone and muscle/total fat ratios than females.