The study was aimed at evaluating growth performance, carcass, and non-carcass traits of Horro rams fed on commercial feed (CO) supplemented with different proportions of duckweed (DW). For the study, twenty-four yearling Horro rams initially weighing on average 17.73 ± 0.30 kg were used with a 15-day adaptation period (none-study period) and a 90-day study period. Each animal was randomly assigned to three treatments; T1 (100% CO), T2 (25% DW + 75% CO), and T3 (50% DW + 50% CO) with two replications each containing four animals. All diets were isocaloric and isonitrogenous and formulated according to the nutrient requirements of sheep. The data were analyzed using SAS. Results indicated that dry matter intake in T3 (914.37 g. d-1) was higher (P < 0.001) than in T1 (849.12 g. d-1) and T2 (870.50 g. d-1). Average daily body weight gain in T3 (77 g. d-1) was higher (P < 0.001) than in T1 (48.60 g. d-1) and T2 (58.50 g. d-1). Feed conversion efficiency was higher (P < 0.001) for T3 (0.08) followed by T2 (0.07) and T1 (0.05). Final body weight (24.56 kg), empty body weight (20.40 kg), hot carcass weight (10.27 kg), dressing percentage (42.01) and rib-eye muscle area (9.11 cm2) were higher (P < 0.001) for T3 than for others. Therefore, increasing the inclusion level of supplementary duckweed up to 50% improves growth performance, carcass quality, and yield of Horro ram.