Northeastern Atlantic from the Arctic Seas south to NW Africa Includes also the North Sea and parts of the Baltic Sea.
Hydractinia echinata has also been recorded in the Mediterranean a few times. However, these records give no figures and no voucher material is known. Goette (1916) thinks that Lo Bianco's H. echinata from Naples were in fact H. inermis [more likely H. fucicola, as Goette misidentified his H. fucicola as H. inermis]. Therefore, there remain some doubts on the correct identification and the presence of H. echinata in the Mediterranean needs confirmation.
The species has also been recorded from the western Atlantic, but these records refer to other species as has been shown by Buss & Yund (1989). Type locality: British Isles.