Abstract Background Local governments increasingly implement outdoor smoke-free environments to decrease adolescent smoking and denormalize smoking behavior. Recent research indicates that compliance with smoke-free outdoor spaces is often lacking. We examined compliance with outdoor smoke-free environments and examined the mechanisms that affect compliance in different contexts. Methods We performed a realist review, an exploratory approach that synthesizes existing evidence into a program theory that links elements of compliance with outdoor smoke-free environments with specific mechanisms and outcomes. A search was performed in PubMed, Web of Science, Embase, and PsycINFO, resulting in 25 relevant English language articles. Preliminary results Our analysis showed that the kind of enforcement (voluntary or enforcement with sanction options etc.) influences smokers’ compliance. Additionally, how implementation of the smoke-free environment was done (with supporting signs, size of the environment, attention for smoking cessation etc.) also influenced smokers’ compliance. For instance, with the implementation of an outdoor smoke-free environment (context), smokers get used to non-smoking. They are reminded they can quit smoking at any time (mechanism), leading to more compliance (outcome). If however, their social environment continues smoking (context), they are more inclined to keep smoking (mechanism), which leads to less compliance (outcome). Conclusions Compliance of smokers with smoke-free outdoor environments is influenced by the type of enforcement and the type of outdoor smoke-free environment. These mechanisms are important to understand so that policymakers may consider smokers’ reactions and are better able to anticipate upon them. Key messages • Type of enforcement and type of implementation influence compliance with smoke-free outdoor environments. • This realist review helps policymakers consider smokers’ reactions while implementing smoke-free environments.