The inhibiting action of 5-[hydroxy(phenyl)methyl]-6-methylpyridazin-3(2H)-one (HPMP) on the corrosion of copper in nitric acid has been studied. The results from weight loss and electrochemical impedance measurements consistently identify HPMP as a good inhibitor. Impedance spectroscopy revealed that the corrosion of copper in nitric acid solution was influenced to some extent by charge transfer. The inhibition efficiency increases with increase in inhibitor concentration but decrease with rise in temperature (303-343K). The adsorption of HPMP onto the copper surface was found to follow the Langmuir adsorption isotherm. Various parameters (Ea, DG° ads, Kads) for adsorption reveal a strong interaction between inhibitor and copper surface. The negative values of DG° ads indicate the spontaneous adsorption of the inhibitor on copper surface. Both kinetic parameters (activation energy, pre-exponential factor, enthalpy of activation and entropy of activation) were calculated and discussed.