In 2016, bacterial canker symptoms, often with dried ooze, were observed on Salix alba plants in municipal lands and parks in Kerman and Fars provinces, Iran. To determine the causative agent, samples were collected from symptomatic trees, and macerates of the affected bark tissues were plated on sucrose nutrient agar (SNA). Ten isolates were identified by phenotypic characterization, pathogenicity tests, and two of them further confirmed identity using sequence analysis of the partial of 16S rRNA and gyrB genes, and phylogenetic analysis. The isolates showed the highest identity (99–100%) with Brenneria salicis. To our knowledge, this is the first report of watermark disease on S. alba caused by B. salicis in Iran.