Sphaeroma serratum was first recorded from the Atlantic coast of Europe, later from the Mediterranean and Atlantic coasts of northern Africa and more recently from the Black Sea, southern Africa and western Australia (Kensley 1978, Jacobs 1987). Sphaeroma serratum has been known from Buenos Aires Province since 1964, where it was known only from Mar del Plata harbor (38°08'S, 57°31'W) having been found in samples taken during fouling studies (Bastida 1968, 1971; Bastida et al. 1980). It has since been found as part of fouling communities in other harbors in Argentina, e.g., Puerto Quequen (38°36'S, 58°40'W), Ingeniero White (38°47'S, 62°14'W) and Puerto Belgrano (38°54'S, 62°06'W) (Bastida 1972, Bastida & Torti 1973, Bastida & Brankevich 1982, Martinez et al. 1984). Having colonized these harbor areas, in recent years Sphaeroma serratum has spread to natural rocky areas around Mar del Plata and has become a member of the local intertidal community (Bastida & L'Hoste 1976).
Sphaeroma serratum has not yet been found on the Patagonian coasts, but its chances of colonization are thought to be high. The wide sandy beaches of Buenos Aires probably acted as a natural barrier to the spread of the species southward (Escofet et al. 1979). Sphaeroma serratum has not been recorded from the coast of Uruguay and Brazil, althought the genus is represented in Brazil by three other species, Sphaeroma terebrans Bate, 1866, S. anandalei Stebbing, 1911, and S. walkeri Stebbing, 1905 (Loyola e Silva 1960, Pires 1982). The distribution of Sphaeroma serratum north of Argentina may be limited by the estuary of the Rio de la Plata due to its great extension and the influence of its waters on Argentine and Uruguayan coasts. The method of introduction of Sphaeroma serratum was probably as part of the fouling community on the hull of ships arriving in Argentina. This transportation was observed for Sphaeroma walkeri in Victoria Harbor (Hong Kong) and its dispersal to areas around Hong Kong (Mak et al. 1985). Other methods of transportation could have been by ballast water (Carlton & Iverson 1981) and less probably by pieces of wood floating adrift. Burrowed pieces of wood found in coastal areas are frequently inhabited by specimens of Sphaeroma serratum, which obtain protection in the teredine galleries and holes (Bastida & Torti 1972).
