Ammonia accumulation in the earthen ponds is unavoidable and is considered as one of the serious problems of aquaculture. In this study susceptibility to chronic exposure of sub lethal ::::::union::::::ized ammonia (NH₃) in Caspian roachwas investigated. In this regard, two treatment groups and one control group (with three replicates for each one) were considered. Fish of treatment groups were exposed to 0.2 and 0.02 mg/l ::::::union::::::ized ammonia (NH3),respectively during one month rearing period while no ammonia exposure was done in fish of control group. According to the results, most growth factors in theexposed fish to 0.2 mg/l ::::::union::::::ized ammonia were significantly lower compared to both control group and theexposed fish to 0.02 mg/l ammonia (P&le0.05). In hematology study, hemoglobin, hematocrit, MCH and MCHC counts for theexposed fish to 0.2 mg/l were recorded lower compared to fish of  both control and the exposed fish to 0.02 mg/l ammonia. However, blood MCV index were significantly recorded higherin theexposed fish to 0.2 mg/l ammonia compared to fish of other groups. According to the results of present study although chronic ammonia exposure at 0.2 mg/l concentration did not lead to mortality in Caspian roach, it can be considered as a harmful dosage for growth and hematologic indices in this fish. This is while long-time exposure to 0.02 mg/l ::::::union::::::ized ammonia has no negative effect on growth and hematological indices in Caspian roach fingerlings