In this study, the effects of diet including different levels of olive cake were investigated on the fattening performance, blood parameters, certain slaughtering traits, and carcass quality of lambs. Thirty-six male lambs were used in the experiment. The lambs were randomly assigned to three groups with 12 lambs each. Groups included control, 12.5 and 25% olive cake (OC). The mixed feeds were offered ad libitum. All lambs were also allowed to consume alfalfa hay (83.8gDM/animal/day). The experiment lasted for a period of 56days. The effect of different levels of olive cake was not found different in fattening performance values of lambs in 0-56days (P>0.05). Carcass weight, pH, and yield were not different (P>0.05). While the values of color parameters, cooking loss, tenderness, and ether extract level of longissimus dorsi muscle (MLD) was not found different (P>0.05), it was determined that the levels of olive cake increased the water-holding capacity of meat (P<0.05). Furthermore, although the levels of olive cake were shown to decrease total n-3 and total saturated fatty acids (Σ SFA), they also increased total n-6, n-6/n-3 ratio, total monounsaturated fatty acids (Σ MUFA), and total polyunsaturated fatty acids (Σ PUFA) were not different (P>0.05).