Background Treatment non‐engagement in forensic health settings has ethical and economic implications. The multifactor offender readiness model (MORM) provides a framework for assessing treatment readiness across person, programme and contexts. Aims To answer the following question: Are the internal factors of the MORM associated with likelihood of engagement in groups by patients in forensic mental health services? Method In a retrospective design, associations were investigated between internal factors of the MORM, measured as part of assessment for group participation, and the outcomes of treatment refusal, treatment dropout and treatment completion. Results One hundred and eighteen male patients in a high security hospital consecutively referred for group treatment agreed to participate. Internal factors of the MORM associated with treatment refusals included: psychopathic cognition, negative self‐evaluation/affect and effective goal‐seeking strategies. Those associated with dropouts included emotional dysregulation, low competencies to engage and low levels of general distress. MORM factors associated with completion included: low motivation, ineffective goal‐seeking strategies, absence of psychopathic cognition, high levels of general distress and competency to engage. Conclusions Internal factors of the MORM could be useful contributors to decisions about treatment readiness for hospitalised male offender‐patients. Up to one in three programmes offered were refused, so clinical use of the MORM to aid referral decisions could optimise the most constructive use of resources for every individual. Copyright © 2016 John Wiley & Sons, Ltd.