The effect of replacing soybean meal protein (SBM) by raw linseed meal (RLSM), roasted linseed meal (ROLSM) and autoclaved linseed meal (ALSM) in tilapia diets on growth performance, feed utilization and body composition were evaluated in three separate experiments. SBM protein was replaced by RLSM, ROLSM or ALSM proteins in the 1st, 2nd and 3rd experiment, respectively at replacing levels of 0, 25, 75 and 100% for each experiment. The anti-nutritional factors, trypsin inhibitor, total cyanogenic, total polypenolic compounds and phytic acid in RLSM were determined to be 12.50 mg/g, 0.42 mg/g, 196 mg/100g and 2.90%, respectively. Roasting (140°C for 20 min) or autoclaving (121°C for 20 min) of RLSM totally destroyed cyanogenic glycosides and destroyed 54.80% and 80.40% of trypsin inhibitor, 66.40 and 74.10% of total polyphenolic compounds, 57.24% and 31.38% of phytic acid, respectively. Results of the first experiment indicated that, replacing 25% of SBM protein by RLSM protein in tilapia diets did not significantly affected body weight (BW) or body length (BL) however, the higher replacing levels, 50, 75 or 100% significantly (P