During visiting the alfalfa fields in Sahneh county of Kermanshah province, the symptoms of a disease were observed in the form of galls with variable sizes in the crown part of the plants, which had caused a severe decrease in the growth in the alfalfa fields. The size of the galls varied from a few millimeters to several centimeters and were observed only in the crown. After transfer to the laboratory and microscopic examinations, a species of fungus with the characteristics of Physoderma alfalfae (Pat & Lagerh.) Karling Syn: Urophlyctis alfalfae (Pat & Lagerh.) Magnus was observed with chambers containing numerous resting spores and turbinate cells (Figure 1), which are prominent features of alfalfa crown wart disease cause. The resting spores had a depressed part and their size was 40-55 micrometers in the longer diameter and 22.5-35 micrometers in the shorter diameter. According to the classification of Hibett et al. (2007), this species is placed in the Blastocladiomycota phylum, Blastocladiomycetes order and Blastocladiales order. The fungus was first reported by Viennot-Bourgin et al. in 1970 from Karaj on alfalfa plant, but afterward there has been no other report of the disease or the fungus in Iran. Considering the damage caused by this disease, it is important to pay attention to its monitoring and to study its biological and pathogenic aspects.