Chloroplastic and cytoplasmic alfalfa (Medicago sativa) leaf protein concentrates were tested as dietary replacements for fish meal in practical diets for tilapia fingerlings. Each concentrate was used to replace 15, 25, 35, 45 and 55% of the fish meal protein in diets containing 40% protein. Diets containing cytoplasmic leaf protein gave the best results, with growth rates higher than those obtained with a fish meal-based diet when the plant protein replaced up to 35% of the fish meal protein in the diet; higher inclusion levels of plant protein depressed growth. No mortalities were recorded during the 9-week test period with any of the experimental diets. It was concluded that the alfalfa leaf protein could be included at levels of up to 35% of the dietary protein in feeds for tilapia.