A 14 week experiment was carried out to study the effects of replacing three different levels (33%, 66% and 100%) of berseem leaf meal (BLM) by leucaena leaf meal (LLM) treated in four different ways (drying for 48 h at 60 °C, autoclaved for 15 min, sprayed with 1% sodium hydroxide and incubated with rumen liquor for 24 h). Groups of Nile tilapia, Oreochromis niloticus (L.), fingerlings (5.07 g mean weight) were fed one of 13 isonitrogenous (30% crude protein) and isocaloric (19.67 kJ per g dry matter) diets, with two replicates (10 fish per aquarium) for each treatment. The results indicated that weight gain, specific growth rate, feed conversion ratio and protein utilization parameters were significantly (p < 0.05) increased by the higher percentage of dried or cooked LLM in tilapia diets. On the other hand, the lowest growth performance and feed utilization parameters were observed in the groups fed LLM diets treated with sodium hydroxide or incubated with rumen liquor. Carcass protein and fat increased significantly (p < 0.05) with increasing levels of LLM and simultaneously decreasing ash content.