INTRODUCTION AND AIMS Opioid use disorder has the lowest quality of life (QOL) and highest disease burden of all substance use disorders (SUD). While opioid treatment does improve QOL, it remains below that of the general population. Previous reviews have indicated that exercise offers benefits for QOL, however the evidence in an opioid treatment population is lacking. This study investigates the feasibility and impact of a 10-week exercise intervention on QOL and mood in a residential rehabilitation program. METHODS Participants admitted to an opioid substitution program within the We Help Ourselves (WHOS) rehabilitation service in Sydney, NSW Australia were invited to participate in a 10-week exercise intervention. Participants completed baseline screening assessing QOL, mood, exercise habits, and a fitness assessment. Willing participants then completed a twice weekly program delivered as part of the group therapy program. Sessions typically consisted of bodyweight exercises such as squats and push ups, and boxing. Following the completion of the training program assessments were repeated. Within group pre-post measures for QOL and mood outcomes were analysed using two-way ANOVA. This clinical trial was registered with Australia New Zealand clinical trial registry (ACTRN12622000213741). RESULTS 45 Participants completed baseline assessments with nine participants completing the intervention and follow up assessment. Significant improvements were seen in QOL (p=0.005), Psychological distress (p<.001), and PCL-5 scores (p=.011). Participants performed well in grip strength, but below norms in all other exercise assessments. Exercise capacity improved following the intervention. CONCLUSIONS Exercise programs are both feasible and beneficial when run as part of SUD improving a range of QOL and mood outcomes. Exercise capacity was generally poor, however improved through the course of the study, often nearing population norms. Exercise should be integrated widely as an adjunct therapy for SUD.