Isotope exchange behavior of bis-resacetophenone phenylhydrazone) nickel(II) complex with nickel(II) in tri-n-butyl phosphate and methanol medium has been studied. The studies were carried out at different temperatures varying the concentration of both metal ion and the complex. The results show that the complex is labile in the kinetic sense. Increase in temperature increases the isotope exchange rate. The increase in concentration also results in an enhancement of the rate of reaction.