The Bare-rumped Sheathtail Bat (Saccolaimus saccolaimus nudicluniatus) is an insectivorous bat in Australia, with limited information available on its roosting ecology and breeding behaviour. We observed two roosts occupied by the species at Cairns, Queensland, between 2011 and 2025. Roost Tree 1 supported a colony of over 100 individuals in 2012, functioning as a day roost with bats emerging shortly after sunset. Roost Tree 2 contained 10–20 bats which arrived individually over a 30–40-minute period after dusk in August and November 2025, indicating this tree functions primarily as a night roost. Pups were observed in December 2024 and 2025, indicating that December is the nursing period for this population. These observations explain why bats are rarely observed at Roost Tree 2 before 19:00. Furthermore, hollows appearing vacant during the day may serve important roosting and nursing functions at night.