An experiment was conducted to evaluate the effects of phytase and multicarbohydrase ( MC ) on growth performance, bone ash, and nutrient digestibility in broilers fed a nutritionally reduced diet. A total of 480 Cobb 500 male broilers were randomly allocated to 8 treatments with 6 replicates of 10 birds each. Experimental diets consisted of a positive control ( PC ); a negative control ( NC ) with the reduction of ME, CP, Ca, and nonphytate phosphorus by 75 kcal/kg, 1.5, 0.15, and 0.15%, respectively; NC plus phytase at 500, 1,000, or 1,500 FTU/kg as T3–T5; and further plus MC at 500 mg/kg as T6–T8. Results showed that during 0–18 d of age, feed conversion ratio ( FCR ) was increased ( P < 0.05) in the NC group compared with the PC group; this was recovered ( P < 0.05) in T5 group; BW gain ( BWG ) was increased ( P < 0.05) in T6–T8, and FCR was decreased ( P < 0.05) in T6 and T8, compared with the NC group. For bone mineralization, fat-free dry weight, weight, percentage, and concentration of tibia ash were decreased ( P < 0.05) in the NC group compared with the PC group; T3–T5 increased ( P < 0.05) tibia ash percentage and concentration, compared with the NC group, but only the tibia ash percentage reached to the level that of the PC group; T6–T8 increased ( P < 0.05) tibia ash weight, percentage, and concentration compared with the NC group. Similarly, nitrogen retention and AMEn were decreased ( P < 0.05) in the NC group and recovered in T3–T8; ileal P digestibility also was increased in T3–T8, to a greater level than that in the PC group. The results from contrasts suggested increasing phytase level with or without carbohydrase linearly increased broiler BWG, FCR, bone mineralization, N retention, and ileal P digestibility. Moreover, when combined with carbohydrase, increased phytase level in the diet linearly increased broiler energy utilization, while phytase alone showed no effect on AMEn. In conclusion, supplementation of a combination of phytase and MC could compensate the decreases in growth performance, bone ash, and nutrient digestibility caused by a nutritionally reduced diet.