This study was designed to determine the maximum replacing levels of fish meal (FM) by a plant protein mixture (PPM) in eight diets for Nile tilapia. The PPM consisted of cottonseed, sunflower, canola, seasme and linseed meals.FM in the basal diet was replaced by PPM in the diets at a replacing levels of 15,30, 45, 60, 75, 90 and 100%. A total number of 480 Nile tilapia were randomly distributed into eight treatments, each in three replicates.After 12 weeks of feeding, results revealed that replacement of 15, 30 or 45% of FM by PPM did not significantly affect feed intake (FI), feed conversion ratio (FCR), protein efficiency ratio (PER), and the apparent digestibilities coefficient (ADC) of dry matter (DM), crude protein (CP) and ether extract (EE), while the higher replacing levels (60, 75, 90 or 100%) significantly
(P<0.05) reduced these parametesr. Growth parameters were relatively parallel to those of FI, FCR and PER, whereas replacement up to 45% exhibited body weight (BW), body length (BL), weight gain (WG) and specific growth rate
(SGR) not differing significantly (P<0.001) from the fish fed on control diet.Compared to control diet, increasing PPM in the diets significantly reduced hemoglobin, hematocrit and increased the activity of alanine aminotransferase
(ALT) and aspartate aminotransferase (AST). The incorporation of PPM in diets did not significantly affect the whole-body dry matter (DM) and crude protein (CP).From economic point of view, replacement of FM by PPM up to 45% in
tilapia diets reduced feed costs/kg diet and feed costs/kg weight gain by 11.40 and 6.74%, respectively.