This study was aimed to assess the possibility of partial replacement of wheat flour and corn meal with Olive pomace (OP) in the rainbow trout diet through evaluating the growth, immunological, and hematological indices as well as the flesh quality. ‎To this end, a total of 3600 rainbow trout (weighting 184±0.7 g) were fed with differecnt levels of OP (2, 4, 6, 8 and 10 wt %) for 63 days, besides a control group without OP treatment. The findings exhibited no significant change in the growth indices of the experimental fish groups when compared to the control group. Among the exprimetnal groups, in general, the fish received 10% OP demonstrated the highest alterations. whereas the activity of superoxide dismutase, lysozyme, monocyte and neutrophil considerably increased when compare to the control treatment. Generally, OP inclusion decreased and increased, respectively, the saturated and unsaturated fatty acid contents of both liver and carcass tissues, especially at the higher levels. Taken together, OP could improve both health state and nutritional values of fish and the findings suggested the feasibility of partial OP replacement in the diet of rainbow trout.