We examined habitat use and foraging activity of the endangered Hawaiian hoary bat (Lasiurus cinereus semotus), as well as nocturnal aerial insect abundance at Kaloko-Honōkohau National Historical Park located in the coastal region of Kailua-Kona, Hawai‘i Island. We evaluated bat activity in two habitat types, wooded shorelines beside brackish water fishponds and xeric lava fields dominated by two invasive plant species: white leadwood (Leucaena leucocephala, Fabaceae), and fountain grass (Cenchrus setaceus, Poaceae). We recorded bat echolocation calls at seven acoustic stations that operated nightly from November 2013 through February 2015. Additionally, three UV light traps were used to collect insects at three locations from dusk to dawn in January, April, July and November 2014. Bat acoustic activity showed seasonal patterns in pulse counts, call-events, feeding buzzes and frequency of occurrence with three major peaks in bat echolocation activity in November–December 2013, April–May 2014, and August–December 2014. Overall, bat acoustic activity was greatest at the shoreline of Kaloko Fishpond. Although there were no significant differences in insect biomass among collection stations, Hawaiian hoary bats use the Park as an important foraging habitat.