We detected a maternity roost of Eptesicus brasiliensis in a large liana at Cocha Cashu Biological Station (Peru). Our objective was to describe the roost and its surrounding habitat employing visual methods to estimate colony size and time of foraging. At least 10 adults (9♀, 1♂) and one juvenile used a cavity in a liana that hung across a small trail. We used a night vision scope and infrared camera traps to note that bats left the roost for short foraging bouts (<1 hr). We also discuss the potential importance of lianas as roost sites in tropical forests.