Bats play an important role in regulating ecosystems, and seasonality has great influence on their reproductive cycle and storage status of bodily energy reserves. Aiming at a better understanding of the dynamics of these processes, male little yellow-shouldered bats (Sturnira lilium) were captured during both the dry and rainy seasons and their reproductive and metabolic patterns were established. Testes were processed histologically for morphometric analysis by light microscopy. Plasma glucose and testosterone concentrations were determined, as well as liver and muscle glycogen, lipids, and protein. Data showed little variation in testicular morphometrical parameters and also in body energy reserves between the seasons evaluated. We conclude that occasional season variations in bodily energy reserves in S. lilium do not seem to present a major influence on testicular morphometry in this species, which may reflect a successful adaptation of S. lilium to its habitats.