Global warming, water salinization, and increased anthropogenic usage of freshwater sources have had severe effects on water sources and aquaculture practices, which is consequently putting pressure on aquatic fauna and fish production. Hence, brackish water can be used as an alternative and sustainable approach to meet the increasing food requirements. Four groups with triplicates were designed to evaluate the impact of brackish water on Cirrhinus mrigala (n = 100) for 180 days; T-0: control group (freshwater), T-1: (5.45 ppt salinity), T-2: (8.45 ppt salinity) and T-3 (12.45 ppt salinity). Little behavioural alterations and normal feeding were observed in all experimental groups as compared to control group, except group T-3. Survival rate was 100 % in all groups excluding group T-3, which had shown 88 % survival rate (P < 0.05), while mean weight gain and length gain were observed better with low FCR in T-1 and T-2 groups (P < 0.05) but best growth rate observed at 5 ppt salinity level. Significant reduction in haemoglobin (Hb), hematocrit (HCT), red blood cells (RBCs) and increase in white blood cells (WBCs) and platelets (PLTs) was observed in group T-3 compared to other experimental groups (P < 0.05). ALT, AST, ALP, urea, creatinine, and triglycerides, exhibited significant changes in T-3 group after 180 days (P < 0.05). Erythrocytes had shown morphological alterations as; micronuclei, notching, blebbing, pear-shaped nuclei and spherocytes in T-3 group. Significant increase in DNA damage in various tissues had indicated potential genotoxic impact of highly saline brackish water. Oxidative stress markers were increased significantly and antioxidants reduced (P < 0.05) at high salinity level brackish water (T-3) until 180 days. In conclusion, C. mrigala can potentially grow well in brackish water system at 5 ppt salinity whereas, rise in salinity level (12 ppt) is detrimental to freshwater fish health and growth.