This experiment was conducted to determine the effect of feeding leucaena forage and silage substitution in concentrate on the performances of dairy cows. Nine cross-bred Holstein Friesian cows (410±12kg) in the 12th week of lactation were randomly allocated to one of three treatment groups with three replicates/treatments in a completely randomized design. The three treatments were control diet without substitution of leucaena forage and silage (DLFS0), diet with substitution of leucaena forage 10% (DLF10) and diet with substitution of leucaena silage 10% (DLS10). Cows were fed treatments for 60 days. Although nutrient intakes were not significantly different (p>0.05) each other, digestibility of DLFS0 was significantly higher (p<0.05) than others. Conversely, nitrogen utilization and average milk yield of cows offered DLFS0 were significantly lower (p<0.05) than those of cows fed on DLF10 and DLS10. The highest feed cost (p<0.05) per kg of milk was found in DLFS0 and the lowest cost was observed in DLF10. Therefore, although the leucana forage and silage could be substitute up to 10% of concentrates without adverse effects on the performances of dairy cows, the substitution of leucaena forage gave the better performances than that of leucaena silage.