Zagros is a mountainous region in western Asia, extending roughly along the western borders of Iran. In the past few years oak decline in the Zagros region has become a serious national concern in Iran, with multiple factors seemingly acting as causal agents. During field surveys recently made in central Zagros, signs of canker trunk rot on oaks and considerable damage were observed, caused by a resupinate polypore identified as Inonotus krawtzewii, previously known from the Russian Far East, China and central Europe. The identity of the fungus was confirmed by analyses of morphological characters and sequences of the nuclear ribosomal ITS region. A description of the species and illustrations are provided, and the symptoms are discussed. A key is given to the known resupinate species of Inonotus developing under bark. This is the first report of I. krawtzewii from western Asia and on Persian oak, and the first report of its invasiveness, at least partly contributing to the Zagros oak decline.