The native habitat of the brown bullhead Ameiurus nebulosus is located in the eastern part of North America. This species was introduced in Europe, Southwestern Asia and New Zealand. It was supposed that it entered Russia from the southwest and now inhabits some water bodies at the border with Ukraine and Belarus. Information about bullheads in Russia was searched for in scientific editions and angler’s blogs. Anglers’ reports have been verified by survey and fishing. It turned out that brown bullheads did in fact appear in Russia, but not where they were expected: they were found by the city of Saint Petersburg on the Karelian Isthmus, i.e., on the territory between Lake Ladoga and the Gulf of Finland of the Baltic Sea. They inhabit at least three lakes. This invasion resulted from release by unauthorized individuals. The revealed habitats are linked by brooks with the river systems of the Baltic Sea Basin. The following spread of the brown bullhead is possible due to intentional releases and natural processes.