The phase of the moon is well known to affect activity patterns of animals at night, and may also affect visibility for motorists. However, surprisingly little is known about whether moon phase is correlated with frequency of wildlife-vehicle collisions (WVC). We investigated the relationship between frequency of WVC at night and lunar phase for four common large ungulate species that account for significant numbers of serious WVC along roads in agricultural and forested landscapes: wild boar Sus scrofa, roe deer Capreolus capreolus, and red deer Cervus elaphus in Castile and Leon, Spain, and white-tailed deer Odocoileus virginianus along roads in New York State, USA. Three of the four species were more frequently involved in WVC around the full moon phase of the lunar cycle; this pattern was evident throughout the year but strongest in winter. Roe deer, the species with WVCs that were mostly closely associated with the lunar cycle, had a frequency of WVC involvement that was 71.3% higher during the full moon than new moon period. Our results indicate that rates of nocturnal ungulate WVC cycle on a period of a lunar month, which has implications for traffic safety planning and for preparing emergency responses for WVC.