PURPOSE: Insomnia is highly prevalent in prisoners. The purpose of this paper is a review of research evidence on interventions with sleep as an outcome (2000 to 2020) and rates of insomnia prevalence and associated factors in prisons (2015 to 2020). DESIGN/METHODOLOGY/APPROACH: An internet-based search used Medline, PubMed, PsycINFO (EBSCOhost), Embase, Web of Science and Scopus. Seven interventions and eight sleep prevalence or sleep-associated factor papers were identified. FINDINGS: Intervention research was very limited and the quality of the research design was generally poor. Interventions such as cognitive behavioural therapy for insomnia (CBT-I), yoga and mindfulness can be beneficial in a prison setting. This review identified a high prevalence of insomnia in prisons across the world, which was supported by recent evidence. Factors associated with insomnia include anxiety, depression, post-traumatic stress disorder, personality disorder and pain. RESEARCH LIMITATIONS/IMPLICATIONS: There is a need for appropriately powered randomised control trials of CBT-I in prisons and a need to use objective measures of sleep quality. ORIGINALITY/VALUE: Due to a lack of an up-to-date review, this paper fulfils the need for a review of the evidence on interventions in prison settings with sleep as an outcome, rates of insomnia prevalence and associated factors in prisons.