In 2014, potato cv. Agria plants showing leaf spot and blight symptoms on leaves were observed in Ghorveh, Kurdistan Province, Iran. Disease symptoms were observed on more than 2-3% of plants in the potato fields in 3 villages (Dizaj, Hajiabad,and Kazemabad). The causal pathogen was identified as Alternaria cantlous based on cultural, morphological, genetic and pathogenicity analyses. This is thought to be the first report of leaf spot caused by A. cantlous on potato in Iran and the world.