With increased globalization, the spread of alien species is expanding. One such species is the Regal Demoiselle, Neopomacentrus cyanomos; a small, planktivorous damselfish native to coral reefs in the Indo-West Pacific Ocean. In 2013, this species was discovered in the southwest corner of the Gulf of Mexico where it was already well established and is now known to occur throughout the western and northern Gulf of Mexico. This year we found N. cyanomos around the northwestern islands and peninsula of Trinidad, again already well established and inhabiting shallow, rocky outcrops and shipwrecks. Abundances on the nine sites we surveyed ranged from 3 - 100s. At several sites, we saw males courting females, spawning, and guarding egg clutches. We plan to perform genetic analysis to identify relationships between the Trinidad populations, native populations and those in the Gulf of Mexico. Additional future work will be to identify the age and sex structure of the population. We surmise that this species was likely introduced to Trinidad and the Gulf of Mexico via the transport of oil and gas rigs and their support vessels from the Indo-West Pacific. These two locations, the only western Atlantic sites where this species currently is known, are regions with extensive oil and gas industries. Given its spread throughout the Gulf of Mexico, where it lives on coral reefs, and its ability to colonize the estuarine environment of Trinidad, it is also likely that N. cyanomos will start to colonize the southern Caribbean Sea in the near future. The ecological implications of this introduced species are currently not well understood and require further study and observation.