Approximately 65 vessel reefs have been deployed intentionally in Broward County, Florida since 1982. The purpose of these deployments was to enhance fish stocks for recreational fisheries and sport divers. The other main goal was to reduce pressure on heavily exploited natural reefs. Several studies have been conducted at both artificial and natural reef sites in the area; however, none of these have focused on nocturnal fish assemblages (Ferro et al., 2005; Arena et al., 2007). The goal of our study was to characterize nocturnal fish assemblages on vessel and natural reefs in Broward County. This data, in addition to the existing diurnal data, will provide a more comprehensive understanding of fish assemblage structure on artificial and natural reefs. Comparisons among vessel and natural nocturnal fish assemblages and previous diurnal studies were made. Abundance was greater on diurnal natural and vessel reefs when compared to nocturnal. Abundance was also greater on nocturnal vessel reefs than nocturnal natural reefs. The twilight period on vessel reefs was characterized by high abundance of piscivores and a significantly greater abundance of grunts than during the nocturnal period. The abundance of grunts supports their movement during this time to surrounding sand flats to feed. The vertical relief of the vessel reefs seemed to appeal to an abundance of pelagic fishes as well as planktivores. Distinctly different fish assemblages were seen between nocturnal natural and vessel reefs, as well as between diurnal and nocturnal natural reefs and vessel reefs. Fisheries-important fishes were more abundant during the day, but also more abundant on vessel reefs than natural reefs. Although vessel reefs do not mimic the natural reefs studied or support the same fish assemblages, they are providing habitat for diverse nocturnal fish assemblages.