To analyse the evidence of the effectiveness of long-acting injection buprenorphine (LAI-B) in the management of opioid use disorder (OUD). Databases were searched for studies reporting on the effectiveness of LAI-B for the treatment of OUD. Risk of bias was assessed, and a narrative synthesis of data was presented. The study adhered to PRISMA guidelines and was registered with PROSPERO (CRD42023396033). Eighteen studies were included in the final review: two double-blind randomised control trials, two open-label randomised control trials, two retrospective cohort studies, one non-controlled pilot study, and eleven observational studies. In comparative trials, LAI-B was superior to placebo and superior or non-inferior to treatment as usual. LAI-B was positively associated with improvements in abstinence rates and patient-centred outcomes. There was limited data on the long-term effects of continuous LAI-B prescription. LAI-B is an effective treatment for OUD with advantages over existing forms of treatment. Patients reported high levels of medication satisfaction and there were no significant safety concerns. This review highlights the need for future research on long-term effectiveness outcomes, with participants of more varied demographics and psychiatric comorbidity, which is more reflective of the OUD population seen in community clinical settings.