Very thin ZrC films, grown on (100) Si substrates at a temperature of 500 degrees C by the pulsed laser deposition (PLD) technique, were irradiated by 800 keV Ar ions with fluences from 1 x 10(14) cm(-2) to 2 x 10(15) cm(-2). Films structure was investigated using grazing incidence X-ray diffraction technique. High resolution transmission electron microscopy investigations were used to study the microstructural modifications induced by Ar ion irradiation. TEM results showed that ZrC films retained their nanocrystalline structure with average crystalline grain dimensions slightly increased, while the Si substrate was damaged for a fluence of 1 x 10(14) cm(-2) and then amorphized for higher irradiation fluences. The oxide surface layer thickness formed during atmosphere exposure of films slightly increased along with the increase of the irradiation fluence, while the amorphous interface between the deposited film and the crystalline Si substrate disappeared. No major defects, voids or precipitates were found in the irradiated nanocrystalline ZrC films. (C) 2018 Elsevier B.V. All rights reserved.