Abstract: The objective of this study was to evaluate the possible effects of manganese (Mn) exposure on variations of cortisol levels in Garra gotyla gotyla. LC50 value of manganese after 96 hours was found to be 3.2mg/l for Garra gotyla gotyla. Three replicates of 10 fishes were subjected to three sub-lethal concentrations of manganese i.e. 0.64mg/l, 1.28mg/l and 1.92mg/l (20%, 40% and 60% respectively of LC50value of manganese) for 1, 5 & 9 weeks. Blood samples were isolated from the fish following the exposure to measure the levels of cortisol and compared to the control group. We observed significant increase(p<0.01) in the levels of cortisol of three groups of fish after 1st week of exposure to three doses of manganese as well as significant decrease in the cortisol of three groups exposed for 5th & 9thweek. The rate of decrease in group III (exposed to1.92 mg/l of Mn) was higher than that of group I & II (exposed to 0.64 mg/l of Mn and 1.28 mg/l of Mn).