Mammals are an incredibly varied class of vertebrates. From small rodents, such as mice, to large animals, such as elephants, from swimming mammals, such as seals, to flying mammals, such as bats, the range of functional traits, niche occupation, and habitat requirements for mammals is diverse. As such, the impacts of roads on mammals are also diverse. In this chapter, we present the well-known impacts of roads on mammals—road mortality, barrier effects, and habitat loss and degradation—while exploring new and emerging trends in research and identifying gaps in the literature, to provide directions for future research. We argue that, as one of the most studied classes of animals, the existing research on mammals provides a strong foundation of knowledge, and that future studies should strive to “push the envelope” by improving methodological sophistication and study system complexity. This may include exploring the cumulative impacts of roads on mammals on the population- and community-level or at the landscape-scale. Broadening the perspective from which we study the relationship between roads and mammals (and other wildlife) is the necessary next step in understanding the extent of the ecological impacts of roads on the terrestrial environment.