A study was conducted to determine if intake of honey mesquite (Prosopis glandulosa Torr.) leaves by sheep could be increased by supplementing activated charcoal at 0.0, 0.33, 0.67 or 1.00 g / kg of body weight. Twenty wether lambs (36.6 ± 0.6 kg) were randomly assigned to the 4 treatment levels. Lambs were fed low-quality Sudan-grass hay at 2% of BW plus 80 g/d of molasses for 7 d, and Sudan-grass hay at 1.9% of BW plus 80 g/d of molasses mixed with the assigned level of activated charcoal for 16 d (d 8 to 23). On d 8 to 23, lambs were also given ad libitum access to honey mesquite leaves that had been previously harvested, frozen, and thawed immediately before feeding. Repeated measures analyses were used to determine if level of activated charcoal fed to lambs affected daily intake of mesquite leaves. No differences (P = 0.52) in intake of mesquite leaves were detected. Mean intake of mesquite leaves was 20.7 ± 3.7, 23.8 ± 3.8, 20.2 ± 3.7, and 27.3 ± 3.7 g/d for 0.0, 0.33, 0.67 and 1.0 treatment levels, respectively. Consumption of mesquite leaves varied greatly among lambs, ranging from 1.4 to 7.4% of their diet during the last 8 d of the study. No differences in hay intake (P = 0.23) or lamb weight gain (P = 0.58) were detected among supplemental charcoal treatments. Future studies examining the consumption of honey mesquite leaves by sheep should consider the potential variability in intake among individual animals.