The objective of this study was to determine the growth performance of growing and finishing beef steers when fed with a fibrolytic feed enzyme (FFE)in a completely randomized design.This experiment was conducted during growing and finishing periods using 60group-penned Angus crossbred steers randomly assigned to treatments: control (no enzyme), low enzyme, and high enzyme.For the enzyme treatments, the FFE was added to the control diet at a dose of 1 or 2 g enzyme/kg DM TMR for the low-enzyme or high-enzyme treatment, respectively. Supplementing the grow-ing diet with FFE did not affect DMI regardless of dose rate. Body weight gain was not affected by FFE supplementation. Supplementation with FFE did not affect ADG and G:F. The overall growth performance during the finishing period was not influenced by the FFE, as was seen in the growing period. However, supplementation with FFE reduced 12th-rib fat thickness (P < 0.01) and tended to decrease the marbling score (P = 0.14)across both enzyme doses. Supplementing the beef growing and finishing diets withFFE at 1 and 2 g/kg DM TMR did not affect growth performance and had minor effects on the carcass characteristics of beef steers.