The use of dry acacia (Acacia mangium) leaf as protein source in beef ration was investigated using twelve nine month to two year old Brahman steers. Randomized complete block design with three blocks and four treatments was used for this study. Body weight of the Brahman steers was used as blocks while the percentage of dry acacia leaf in concentrate feed at 0, 10, 20 and 30 was used as treatment groups. The Brahman steers were fed for ninety days. The results revealed that average body weight gain, growth rate, and feed conversion ratio of Brahman steers receiving the concentrate feed with different levels of dry acacia leaf were not significantly different (P>0.05). The Brahman steers that received the percentage of dry acacia leaf in concentrate feed at 0, 10, 20 and 30 had average body weight gains of 95.28, 100.00, 82.89 and 93.32 kg/head while average growth rates were 1.06, 1.11, 0.92 and 1.04 kg/head/day, feed conversion ratios were 10.79, 10.01, 10.98 and 9.95, and the total feed cost/kg weight gain were 33.18, 32.11, 30.31 and 28.25 Baht, respectively. Thus, it is possible to use dry acacia leaf up to 30 percent in concentrate feed.