Purpose This review aimed to examine (1) stigmatising attitudes of probation, parole and custodial officers (hereafter referred to as correctional staff) towards people with mental health issues, (2) the potential impacts of these attitudes on client treatment and (3) what is currently known about anti-stigma interventions in correctional settings. Method Academic databases were searched for peer-reviewed and dissertation literature published between 1 January 2000 and 10 February 2022. Eligible studies included observational and intervention studies investigating stigmatising attitudes of correctional staff towards people with mental health issues. The Mixed Methods Appraisal Tool (MMAT) was used to assess the quality of studies. A meta-analysis of anti-stigma intervention studies was performed. Results A total of 35 studies were included for data extraction, including eight interventions, one longitudinal, 18 cross-sectional and eight qualitative studies. Some studies indicated neutral or positive attitudes, but the majority showed a range of stigmatising attitudes towards people with mental health issues. The findings indicate these stigmatising attitudes can lead to negative treatment of justice-involved clients, such as more coercive, restrictive and punitive approaches. The meta-analysis of six intervention studies focussed on education found a small positive effect on stigmatising attitudes (d = .31, 95% CI: 0.16–0.45). Conclusion The various stigmatising attitudes of correctional staff towards people with mental health issues can have detrimental impacts on the well-being and treatment outcomes of clients presenting with mental health issues. Anti-stigma interventions may be effective in mitigating these impacts; however, more rigorous evidence is needed.