The invasion of Indo-Pacific lionfish (Pterois volitans/P. miles) throughout the Caribbean and southeastern U.S. Atlantic represents a significant ecological threat, yet few studies have examined the daily activity and movement patterns of this invasive species. In this study, passive acoustic telemetry was used to track lionfish at 4 coral reef sites in the Florida Keys. Fourteen lionfish were tagged among the 4 sites, and the total number of days tagged fish were detected ranged from 5 to 141 days. Hourly detection data revealed diel activity patterns with peaks at dawn and dusk. Mixed model analysis of detection data indicated a significant effect of time of day, with lionfish activity greater at twilight than during day or night. These results support observations from previous studies that lionfish are most active at dawn and dusk when they are foraging. The 95% kernel utilization distribution home range size ranged from 360-18,812 m 2. Lionfish movements were generally localized, with mean daily distance moved ranging from 24-116 m, although one lionfish had a maximum daily distance moved of 427 m. Short-term activity centers revealed possible diel shifts in micro-habitat use for 2 lionfish, as well as an emigration of one lionfish to an adjacent patch reef ~2 00 m away. These findings increase our understanding of lionfish behavior on coral reefs and highlight the need for more detailed studies examining fine-scale habitat use and movements across more habitat types. The results from this study will further contribute to the spatial information required to improve the effectiveness of monitoring and controlling lionfish populations in the Florida Keys.