The Indo-Pacific Sergeant Abudefduf vaigiensis (Quoy & Gaimard, 1825) (Chordata: Pisces: Actinopterygii: Perciformes: Pomacentridae) is first recorded in the south-central Mediterranean Sea (Libya), based on the external morphology and the barcoding of a fragment of the cytochrome c oxidase subunit I gene. Present sightings from field surveys and social media include juveniles, sub-adults, and a single adult specimen, suggesting that the species is now established in Libyan waters. No certainties occur regarding timing and possible pathway of arrival of this species in the area, and it may have simply gone undetected for years. The joint effort of field studies and citizen science projects in collaboration with international organizations continues shedding light on bioinvasions in Libya, with valuable outcomes for the Mediterranean marine biology as a whole.