Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ. INTRODUCTION: Opioid agonist treatment is effective for opioid dependence and newer extended-release buprenorphine (BUP-XR) injections represent a significant development. The Community Long-Acting Buprenorphine (CoLAB) study aims to evaluate client outcomes among people with opioid dependence receiving 48 weeks of BUP-XR treatment, and examines the implementation of BUP-XR in diverse community healthcare settings in Australia. METHODS AND ANALYSIS: The CoLAB study is a prospective single-arm, multicentre, open-label trial of monthly BUP-XR injections in people with opioid dependence. Participants are being recruited from a network of general practitioner and specialist drug treatment services located in the states of New South Wales, Victoria and South Australia in Australia. Following a minimum 7 days on 8-32 mg of sublingual buprenorphine (±naloxone), participants will receive monthly subcutaneous BUP-XR injections administered by a healthcare practitioner at intervals of 28 days (-2/+14 days). The primary endpoint is participant retention in treatment at 48 weeks after treatment initiation. Secondary endpoints will evaluate dosing schedule variations, craving, withdrawal, substance use, health and well-being, and client-reported treatment experience. Qualitative and costing substudies will examine implementation barriers and facilitators at the client and provider level. ETHICS AND DISSEMINATION: The study has received ethics approval from the St Vincent's Hospital Sydney Human Research Ethics Committee (Ref. HREC/18/SVH/221). The findings will be disseminated via publication in peer-reviewed journals, presentations at national and international scientific conferences, and in relevant community organisation publications and forums. TRIAL REGISTRATION NUMBER: NCT03809143 PROTOCOL IDENTIFIER: CoLAB1801, V.4.0 dated 01 August 2019.