An adult male blue shark, Prionace glauca (L.), caught in July 2000 by a recreational fisherman off Long Island, New York, USA, had a retained fishing hook from a previous capture. The hook penetrated the gastric wall and lacerated the right liver lobe. Macroscopic lesions consisted of transmural gastritis and peritonitis. Alteromonas sp. and Vibrio alginolyticus were isolated from the peritoneal fluid. In addition, a well delineated, sessile mass was found on the otherwise normal serosa of the right testis. Histopathological findings included mesothelial hyperplasia and hypertrophy involving diffusely the gastric, hepatic and parietal serosae, and forming a discrete testicular capsular mass compatible with mesothelioma. In the liver an intrahepatic cholangiocarcinoma, chronic hepatitis, biliary hyperplasia and increased numbers of melanomacrophages were found. In addition organisms compatible with histozoic and coelozoic myxosporeans were found within the skeletal muscle of the abdomen and intrahepatic bile ducts, respectively. This is the third literature report of a liver tumour and the first report of a coelomic mesothelioma from a shark.