A 60-day feeding study with rainbow trout, Oncorhynchus mykiss, was conducted to determine the effects of replacement of fish oil (FO) by unrefined peanut oil (PO) on growth performance, feed utilization, body composition, fatty acid composition and serum biochemical and haematological parameters. Rainbow trouts (51.60 ± 0.75 g) were fed five experimental diets formulated by replacing dietary FO with PO at levels of level 0 (PO 0 ), 1/4 (PO 25 ), 1/2 (PO 50 ), 3/4 (PO 75 ) and 4/4 (PO 100 ), respectively. As a result, the best growth performance was observed in fish fed with PO 0 and PO 50 diet.