The Lessepsian migrant fish Lagocephalus sceleratus is being recorded for the first time from the Sea of Marmara (Turkey). The record is based on a single specimen landed by purse-seine fishing of horse mackerel (Trachurus spp.) as by-catch in November 2014. It is a poisonous fish containing tetrodotoxin (TTX) which is a potent neurotoxin. Morphometric and meristic data of the landed specimen is submitted.