ABSTRACT: Ophiothela mirabilis is native to the Pacific Ocean and has recently invaded the Caribbean and the southwestern Atlantic. In this study, using SCUBA diving techniques, we observed specimens of the invasive O. mirabilis in association with an octocoral host (Leptogorgia punicea) at the equatorial margin in the southwestern Atlantic (03°32′S, 38°47′W). We filled a gap of more than ~1,500 km between the Amazon reefs and the coast of Pernambuco State. The results indicate that O. mirabilis has invaded ~6,700 km of coastline in the southwestern Atlantic in the last 17 years. Moreover, our results support the hypothesis that the consistent color pattern of specimens from Brazil, French Guiana, Saint Vincent, and Tobago indicates the existence of a single lineage proliferating by asexual reproduction. Because the South Atlantic is the most recent of the oceans, as well as a hotspot for tropical biodiversity, much more information on invertebrate bioinvasions in this region is needed.