Scotophilus kuhlii is distributed in many urban environments, yet the ecology of this species is poorly known. The morphology, echolocation call structure, diet, and foraging areas of S. kuhlii were studied on Hainan Island, south China from March to November 2006. Data from 85 individuals indicate that S. kuhlii is a medium-sized bat with 50.41 ± 1.36 ( ± SE) mm forearm length and 19.81 ± 3.47 g body mass. The wing morphology with high wing-loading (11.38 ± 1.95 N/m²) and moderate aspect ratio (6.96 ± 0.75) indicates that S. kuhlii flies fast and forages in open habitat and at the edges of cluttered environments. Echolocation calls of S. kuhlii consist of a fundamental and up to four harmonics, with a dominant frequency of 45.72 ± 2.09 kHz, and call shape suggests that this species is adapted to forage in open environments. Data from mist-netting and acoustic detection indicated that S. kuhlii foraged mainly around the crown of trees and street lights. Nine insect orders were recorded in its diet, with Lepidoptera (97.46%, by frequency) and Coleoptera (64.72 ± 2.37%, by volume) constituting the main prey, together with Hemiptera (19.99 ± 1.25%) and Hymenoptera (9.43 ± 1.14%). There was significant seasonal variation in the diet of S. kuhlii: Coleoptera increased from March to May, and then decreased to August, while Hemiptera and Hymenoptera showed the inverse trend.