Dual-diagnosis strategies are developing in medium secure services in response to both government policies and clinical need and there has been a move towards integrated services for this patient group. Substance use that has been a feature of the index offence must be taken into account as much as psychosis or the offending behaviour. Treatment of dual diagnosis relies heavily on cognitive-behavioural therapies. Relapse in either psychosis or substance use increases risk and re-admission rates to medium security. This paper reviews the literature on family interventions in dual diagnosis and its applicability to forensic mental health inpatient services. As there appeared to be limited direct evidence, various domains were examined and extrapolated to a forensic setting as appropriate. The review indicates the potential for positive outcomes for families following family interventions in dual diagnosis, which may be beneficial in a forensic setting in lowering risk.