Purpose The purpose of this paper is to examine how the role in offender mental health for the probation service described in policy translates into practice through exploring staff and offenders’ perceptions of this role in one probation trust. In particular, to examine barriers to staff performing their role and ways of overcoming them. Design/methodology/approach Qualitative secondary analysis of data from semi-structured interviews with a purposive sample of 11 probation staff and nine offenders using the constant comparative method. Findings Both staff and offenders defined probation’s role as identifying and monitoring mental illness amongst offenders, facilitating access to and monitoring offenders’ engagement with health services, and managing risk. Barriers to fulfilling this role included limited training, a lack of formal referral procedures/pathways between probation and health agencies, difficulties in obtaining and administering mental health treatment requirements, problems with inter-agency communication, and gaps in service provision for those with dual diagnosis and personality disorder. Strategies for improvement include improved training, developing a specialist role in probation and formalising partnership arrangements. Research limitations/implications Further research is required to explore the transferability of these findings, particularly in the light of the recent probation reforms. Originality/value This is the first paper to explore how staff and offenders perceive probation’s role in offender mental health in comparison with the role set out in policy.