The purpose of this study was to determine the effects of replacing fish meal with red lentil meal (RLM) as an alternative plant protein source in diets for juvenile rainbow trout (10.14 +/- 0.04 g mean initial weight) on growth performance and amino acid composition of fish. Four iso-nitrogenous and iso-lipidic experimental diets were prepared to include 15% (RLM15), 20% (RLM20) and 25% (RLM25) of fish meal. At the end of the 60 day feeding trial, the highest mean individual weight gain (30.55 +/- 0.08 g) of fish was found in control group but not significantly different from RLM15. Crude protein level of whole body/fillet gradually decreased with increase in RLM percentages in the diets. Generally, essential amino acid (EAA) profiles of whole body/fillets reflected the dietary EAA profile. EAA profile of fish fed RLM15 diet was close to control group (P>0.05). However, lysine levels of fish decreased with increasing dietary RLM levels. RLM20 fed fish had the highest body contents of phenylalanine (P<0.05). Naturally, EAA levels of fillets were higher than whole body's EAA levels. Histidine levels of fillets were highest in control group and the lowest in RLM20 group. In contrast, isoleucine levels of fillets were highest in RLM20 group whereas the control group had the least level (P<0.05). Leucine and valine values of fish fed the control diet were lower than the other experimental groups. Threonine level was highest in fish fed the RLM25 diet (P<0.05). Results of the present study showed that 15% of dietary fish meal can be replaced by RLM in diets of juvenile rainbow trout without any adverse effects on growth performance and body amino acid composition.