Sperm morphometry and structure provide useful information regarding the reproductive physiology of a species, which is especially important for marine mammals where information on the spermatozoon is limited. In this study, we investigated the morphometry and structure of the Florida manatee (T. manatus latirostris) spermatozoon. Sperm were retrieved postmortem from the vas deferens of nine adult males classified as “fresh” at necropsy (<24 hr postmortem). Samples were analyzed by automated sperm morphometry analysis (ASMA), laser-scanning confocal microscopy (LCSM), and electron microscopy to assess morphometry and structure, respectively. Morphometric parameters analyzed in this study were approximately 1.5-2 times larger than those previously reported for the Florida manatee. Structurally, sperm had strong localization of F-actin along the midpiece, the axoneme contained four enlarged outer dense fibers (1,5,6, and 9), and midpiece volume was similar to other species that exhibit a multi-partner mating system. Combined, these features may highlight how sexual selective pressures have shaped sirenian sperm morphology and may provide further evidence for the possible occurrence of sperm competition in this species. This is the first study to provide extensive morphometric and structural analysis of the Florida manatee spermatozoon and the results continue to add to the increasing information on male reproductive physiology, which is critical for effective management and conservation of this threatened marine mammal species.