Clinostomum (C.) complanatum is one of the trematode helminthes in birds and causes incidental infection in human. A black-tailed gull (Larus crassirostris) was referred to the Jeju wildlife rescue center. Because of the death of bird after two weeks treatment, necropsy was performed to the bird. Grossly, many living worms adhered to the oral mucosa including pharynx and esophagus were observed. The worms removed were identified as C. complanatum after morphological observation. The linguiform adult worms were $5.19{pm}0.48mm$ long and $1.80{pm}0.18mm$ wide. Histopathologically, severe necrosis and surrounding inflammation were observed at the infection sites of adult worm in pharynx and esophagus. This is the first report for C. complanatum infection in wild black-tailed gull in Korea.