An invasion is currently unfolding at a rate and magnitude never before documented in a marine system. Indo-Pacific lionfish, first reported on western Atlantic coral reefs in 2004, have since spread around the Caribbean region. My group was the one of the first ‘in the water’ to quantify the ecological impacts of this invader on native fauna. I present the story as we understand it so far: comparisons with the native range, predation rates and prey decline, predictions of future impacts, effectiveness of potential mitigation strategies, and some glimpses at our most recent findings on indirect impacts. The lionfish invasion is likely to have long-term ecological and economic implications.