Co-60 gamma irradiation effects on physical, chemical and electrical characteristics of HfO2/Si thin films have been investigated in details. The variations on the crystallographic structure and surface morphology of the films under irradiation exposures were characterized by using X-ray diffractions (XRD) and Atomic Force Microscopy (AFM) measurements. The irradiation influences on the electrochemical structure of the films were analyzed by X-ray photoelectron spectroscopy (XPS) for various depths of the HfO2/Si films. Capacitance-voltage (C-V) and Conductance-voltage (C-V) measurements were performed to study electrical characterization. The correlations through physical, chemical and electrical characteristics have also been discussed in details. The results show that crystallization of the HfO2 thin films and their surface roughness values have been enhanced slightly with increasing in irradiation doses. The passivation of the dangling bonds and generation of the possible trap centers have been observed under the irradiation exposures in XPS measurements. The electrical characteristics of the films slightly change with the irradiation exposures. The results show that the passivation has crucial effects on the radiation tolerance of the HfO2 thin films.