Succinate dehydrogenase is the oxidative enzyme which was drastically affected by the action of heavy metals. Succinate dehydrogenase is chosen as a representative of metabolic enzyme. It is a marker enzyme for detecting the presence of TCA cycle in tissues. The aim of the present study is to assess the enzyme succinate dehydrogenase activities in gill, liver, kidney, brain and muscle of the fish Labeo rohita exposed to sublethal concentration of nickel chloride 1/5th (high), 1/10th (medium) and 1/15th (low) of the 96 hour LC50 values for the period of 10, 20 and 30 days. The fish exposed to nickel chloride showed a decrease the enzyme succinate dehydrogenase activities for 10, 20 and 30 days in gill, liver, kidney, brain and muscle. However, no information is on record concerning the three different sublethal concentration of heavy metal, nickel chloride on the enzyme succinate dehydrogenase of freshwater fish Labeo rohita. The objective of the present work was to observe the effect of nickel on succinate dehydrogenase activities in gill, liver and kidney of Indian major carp, Labeo rohita.