Thirty-six castrated, seven months-old Hanwoo steers (initial body weight: 184 ± 5.2kg) were assigned to three treatments over 23 months to evaluate the effects of supplementation with bentonite (0, 0.1 and 0.3%) on growth performance and carcass and meat characteristics. A completely randomized design with three replicates was used. The inclusion of a bentonite-supplemented diet had an influence on final weight, total weight gain, and average daily gain. Bentonite supplementation had no significant effect on proximate composition and meat quality. For carcass characteristics, there were no significant differences in yield traits and quality traits between treatments (but not cold carcass weight, marbling score, and quality grade). It was concluded that supplementation with bentonite (0.1 and 0.3%) improved growth performance, cold carcass weight, marbling score and quality grade compared with the control, except for meat quality.