Background <p>An active lifestyle has been proven to affect health positively. Active travel—e.g. walking or cycling in everyday life—can make a decisive contribution to an active lifestyle and planetary health. Despite the benefits of active travel, there is a lack of understanding of how built and socio-cultural environmental factors influence its practice. Against this background, this review systematically analyses the influence of these factors based on a social-ecological model.</p> Methods <p>A systematic literature search according to the PRISMA guidelines identified longitudinal studies (2013-2024) investigating the influence of environmental factors on active travel in adults. Ten studies with a total of 35,437 participants were included.</p> Results <p>The built environment proved to be an important factor. Improved infrastructure, such as cycle paths, street lighting, public transport connections, and workplace facilities, encouraged active travel—depending on actual usage and individual attitudes. Socio-cultural influences such as social norms also tended to have positive effects in a few studies.</p> Discussion <p>The built environment influences active travel, whereas there is a considerable need for research on the socio-cultural environment due to the small and inconsistent number of studies. A combination of both factors appears promising, as the interaction of both environments can promote a sustainable change in behavior towards active travel.</p> Conclusion <p>To promote active travel in the long term, urban planning measures should be combined with targeted socio-cultural interventions. Policy and planning should develop integrated measures that address both infrastructure and social conditions.</p>