The red lionfish (Pterois volitans) was first recorded in Martinique on 1 February 2011. Three years later, despite control measures to prevent the increase of lionfish population densities, the species is now well established. Maximum density has reached 1320 individuals ha−1 in some locations and the maximum fish size of 41 cm total length has been observed. A monitoring program was initiated by the Marine Institute of Martinique (OMMM) in 2011 to monitor the invasion and adjust local control efforts. Our results highlight how fast lionfish have been able to invade new littoral areas, especially hard bottom habitats. It took two years for them to completely colonize the west coast of Martinique, despite increasing capture efforts. It is expected that small-scale fisheries would target lionfish. Coastal ecosystems are clearly being subjected to a new threat, which may negatively affect local biodiversity.