In this study, the effects of different replacement levels of earthworm meal (Eisenia fetida) with fish meal with and without garlic powder on growth performance, carcass composition and digestibility of Rainbow trout (Oncorhynchus mykiss) were studied over 8 weeks. For this purpose, different replacement levels of earthworm meal with fish meal including 0, 25, 50 and 75 % with or without 2.5% garlic powder were used. Fingerlings with mean initial weight of 30±0.27 g were distributed in a completely randomized design with four treatments (three replicates) in the same conditions. During rearing period, mean temperature and oxygen level were 12.28±2.14˚C and 6.32±1.12 mg/l, respectively. At the end of trial, growth indices, carcass composition and digestibility were determined. Addition of earthworm meal in diet caused to significant decrease in final body weight, specific growth rate and increase feed efficiency ratio, conversely addition of garlic powder caused to significant increase in final weight, specific growth rate and decrease feed efficiency ratio (P<0.05). Garlic powder effect on carcass composition was not significant but with increasing the earthworm meal levels, body moisture and lipid content deceased and protein and ash content increased (P>0.05). Dried material’s digestibility didn’t have any significant difference by earthworm meal replacement from 0 to 25% (without garlic) (P>0.05) and significantly deceased in 50% inclusion level (P<0.05). Addition of garlic powder caused to significant decrease in each replacement level (P<0.05). Digestibility of lipid and protein had significant increase in diet containing earthworm meal compare to control group (P<0.05), but garlic powder supplementation couldn’t significant effect on lipid and protein (except 50 % replacement level) digestibility in each replacement level (P>0.05). Results showed that earthworm meal can replaced with fish meal in rainbow trout diet up to 50% together with 2.5% garlic powder without any adverse effects on fish growth performance.