Damping-off symptoms were frequently observed on young plants of coastal hogfennel (Peucedanum ja- ponicum) grown in a farmer’s vinyl greenhouse located in Goseong, Gangwon Province, Korea during a dis- ease survey in June 2019. Incidence of the diseased plants was 50-70% in the vinyl greenhouse investigated during the disease survey. Eight isolates of Rhizoctonia sp. were obtained from the diseased plants. All the isolates were identified as Rhizoctonia solani AG-4 based on the morphological characteristics and anastomo- sis test. Three isolates of R. solani AG-4 were tested for pathogenicity on coastal hogfennel by artificial inocu- lation. All the tested isolates induced damping-off symptoms on the inoculated plants. The symptoms were similar to those observed in the farmer’s vinyl greenhouse investigated. This is the first report of R. solani AG-4 causing damping-off in coastal hogfennel.