Loggerhead sea turtles Caretta caretta are globally endangered. The population nesting in Cabo Verde is genetically distinctive and numerically important in a global context. In Cabo Verde, the majority on the nesting takes place on the island of Boavista, but recent work suggests that other important nesting sites may exist. Santa Luzia is the only large uninhabited island in Cabo Verde. In this study, beach surveys revealed 289 nests in 2011, 1817 nests in 2012, and 563 nests in 2013, which means that Santa Luzia may host more than 1% of the loggerhead nesting population in the Atlantic. The sex ratio of turtle hatchlings currently being produced on Santa Luzia is female biased, but there is still a good production of males. The results highlight the importance of the island of Santa Luzia for the conservation of loggerhead turtles, particularly considering that unlike other islands in Cabo Verde, this is a nature reserve where no beach development is taking place and where nest and female poaching is well controlled by the activities of conservation organizations, such as the nongovernmental organization Biosfera 1.