The intensification of artificial light in cities has been identified as a key global threat to biodiversity. Insectivorous bats in urban areas are likely to be some of the most affected species, with a global pattern emerging of slower flying species being most at risk. Remnant patches in cities are critical habitat for bats, therefore identifying a need to understand how we are disturbing this habitat with our public lighting policies and decisions. We aimed to determine if artificial light at the bushland edge affects the activity or diversity of insectivorous bats, and whether light affected the peaks in activity of these urban bats. We acoustically surveyed the interior and the edge of 32 remnant patches with Anabat II detectors. Of the 32 sites, half had mercury vapour lights along the edge sampled, and half had dark edges. At sites where slow flying bats were present, they were significantly more active at dark edges than at light edges. Artificial lights at the bushland edge negatively affect the activity of slow flying bats. The activity peaks of these slow flying bats, however, was affected less by light and more by habitat structure; dark and light habitat edges both supported crepuscular activity, whereas interior bushland sites supported a unimodal peak of activity. Our findings show that light penetration into essential bushland remnants has a negative impact on bat diversity. Our research also highlights the importance of protecting dark interior remnants in cities to conserve the natural activity patterns of nocturnal urban fauna.