AbstractBackgroundTo date, there has been no review of the research evidence examining smoking cessation among homeless adults. The current review aimed to: (i) estimate smoking prevalence in homeless populations; (ii) explore the efficacy of smoking cessation and smoking reduction interventions for homeless individuals; and (iii) describe the barriers and facilitators to smoking cessation and smoking reduction.MethodSystematic review of peer-reviewed research. Data sources included electronic academic databases. Search terms: ‘smoking’ AND ‘homeless’ AND ‘tobacco’, including adult (18+ years) smokers accessing homeless support services.ResultsFifty-three studies met the inclusion criteria (n = 46 USA). Data could not be meta-analysed due to large methodological inconsistencies and the lack of randomised controlled trials. Smoking prevalence ranged from 57% to 82%. Although there was no clear evidence on which cessation methods work best, layered approaches with additions to usual care seemed to offer modest enhancements in quit rates. Key barriers to cessation exist around the priority of smoking, beliefs around negative impact on mental health and substance use, and environmental influences.ConclusionsHomeless smokers will benefit from layered interventions which support many of their competing needs. To best understand what works, future recommendations include the need for consensus on the reporting of cessation outcomes.