The fragmentation of forests by agricultural expansion, urbanisation and road networks is a global phenomenon. In Southeast Asia, wildlife populations are being isolated into pockets of natural habitat surrounded by road networks and monoculture plantations. Mortality by wildlife-vehicle collisions (WVCs) is causing a decline in many species of conservation priority in human-modified landscapes. This study is the first in Malaysia to investigate factors affecting the occurrence of WVCs. We assessed roadkill data gathered by the Department of Wildlife and National Parks on small, medium and large mammals in Peninsular Malaysia. We examined the relationship between wildlife road accidents and environmental factors. We found a total of 605 roadkills, involving 21 species. Roadkill records included three species classified as endangered. Road type, year, and distance from continuous and fragmented forests were significant for determining mammal mortality. Unexpectedly, the majority of road mortality occurred on oil palm plantation roads compared to highways. Mortality of small and medium mammals was greater at locations further away from continuous forest than those closer to forests. Segmentation of continuous forest by roads should be avoided wherever possible, and wildlife corridors should be put in place to reduce the threat of roads on crossing wildlife.