The Hawaiian hoary bat (Lasiurus cinereus semotus), a federally and state listed endangered subspecies, is the only extant native terrestrial mammal in the Hawaiian archipelago. It is an insectivorous, solitary and foliage-roosting species that generally roosts alone or in mother-pup family groups. A total of 58 bats (17 female; 41 male; 56 adult; 2 juvenile) were captured at multiple locations on the east side of Hawaii Island from May 2018 through September 2019. Radio transmitters were affixed to 56 bats including two individuals that were recaptured and radio-tagged twice. When possible, radio telemetry was used to locate bats in trees and forest stands used for day-roosting. A total of 23 trees were identified as bat day-roosts and used by 18 radio-tagged bats (10 male; 8 female; 17 adult; 1 juvenile). Additional bats were tracked to a broader scale; in total 45 bat day-roosts were identified to the level of forest stand and these were used by 33 radio-tagged bats (23 male; 10 female; 32 adult; 1 juvenile). Of these 33 bats, fidelity to a roost tree or stand, as measured by the number of distinct days with confirmed occupancy, ranged from 1 to 15 days (mean = 5.0 days). The use of multiple roosts at the stand-level were observed for eight bats. Three maternity roosts were confirmed and two were monitored using acoustic recording and thermal video stations. Finally, bats confirmed as present at a roost tree were used as “targets” to evaluate the efficacy of detecting bats with thermal imaging, and when not effective (i.e., during hotter parts of the day when the technique could not discern bats from warm vegetation), visual searching with binocular was also investigated. Bats were detected in 30 of 95 (32%) trials. This data release consists of six tabular datasets: roost tree metrics, roost stand metrics, roost fidelity, maternity roost acoustic monitoring, maternity roost thermal video monitoring, and roost detection trials.