Aims: International statistics show that relapse rates associated with opiate and crack cocaine (OCC) misuse remain high. This has led to an increased scientific interest in the topic of relapse. However, there are limited studies reflecting on the state of this field. This review provides an overview of the topic and directions for future research. Method: Guided by the overall question of how relapse into OCC misuse is understood, a scoping review was conducted using Arksey and O’Malley’s framework. A total of 126 studies between 1972 and 2019 were included. The literature was thematically grouped into relapse definitions, theories, associated factors and treatment approaches. Results: This review found that the majority of relapse understandings were derived from the USA and UK, and that these studies predominantly used quantitative research designs. Relapse definitions were controversial with the majority using biomedical concepts of disease. Theories on relapse were based on psychological theories and developed through clinical and neuroscientific research. Findings show that the majority of the literature focussed on relapse risk factors with very few papers focussing on protective factors. Findings on treatment approaches indicate a steer towards harm-minimization strategies over relapse management strategies. Conclusions: This review demonstrates that drug relapse research needs to grow more diverse, inter-disciplinary and user-centred in perspective so as to respond to relevant challenges ahead.