Introduction: In alcohol use disorder (AUD) treatment, evidence-based practice involves the use of validated, standardised assessment tools to gather reliable information about symptoms and functioning. However, due to time constraints and administrative burden, many practitioners do not routinely use them. To overcome these barriers, a freely-available, theory-driven instant assessment and feedback system (iAx) was co-developed with practitioners. Responses are instantly scored and benchmarked against clinical norms for immediate interpretation by the practitioner and discussion with patients. The aim of this study was to evaluate the implementation of iAx at a specialist alcohol and drug outpatient unit in a public hospital. Method: Implementation evaluation was guided by Proctor et al.'s [1] implementation framework and the Getting Research into Practice framework (Joanna Briggs Institute). Baseline (12 months pre-implementation) and follow-up (12 months post-implementation) clinical audits collated records from 313 patients with AUD across 2616 treatment sessions on administration of standardised assessments. Implementation outcome feedback on iAx acceptability, appropriateness and feasibility was obtained from practitioners and patients. Results: The use of validated, standardised instruments as part of initial assessment significantly increased (51% -> 89%; P <0.001). Standardised assessments were also more frequently used in subsequent treatment sessions to monitor patient progress (28% -> 84%; P <0.001). There was preliminary evidence of improved patient outcomes, with treatment program completion rates doubling post-implementation (P=0.001). Practitioners and patients reported high levels of satisfaction with the iAx. Discussions and Conclusions: This study found support for the successful implementation of an electronic, theory-driven iAx system to improve compliance with evidence-based assessment practices in AUD treatment. Preliminary evidence for improved patient outcomes was also found, consistent with the psychological treatment literature. Implications for Practice or Policy: Freely-available software like iAx, co-designed with practitioners, can facilitate evidence-based assessment practices in real-world clinical settings. Disclosure of Interest Statement: This study was supported by a Metro South Study, Education and Research Trust Account MSH Research Support Scheme grant (RSS_2019_007). MJG is supported by a Medical Research Future Fund Translating Research into Practice Fellowship (1167986).