We hereby provide new distributional data for alien and possible alien molluscs from the Italian seas, together with a brief review of their known Italian distribution and updated distributional maps. In particular, Haminoea cyanomarginata is confirmed for the Calabrian shores of the Strait of Messina area and is first reported from eastern and western Sicily, therefore suggesting a natural spreading into the Italian central Mediterranean Sea. Melibe viridis is confirmed for the Ionian Calabrian shores and Sardinia, where it was previously known from isolated records only. Pinctada imbricata radiata is first reported as naturally widening its distribution in Sardinia and in the Gulf of Taranto, where new populations are soon awaited, whilst Aplysia dactylomela is now expanding its range along the Italian Adriatic shores. And last, recent records of Anadara transversa from the Sabaudia Lake testify the role of lagoon systems as hot-spots for the introduction and secondary spreading of alien species, and indicate mussel aquaculture as the likely vector of introduction for its occurrence.