© 2019 Society for the Study of Addiction Aim: Aims were to test the effectiveness of an organizational change intervention integrating smoking cessation treatment into usual alcohol and other drug (AOD) treatment, compared with usual care, on (1) 7-day point prevalence abstinence (PPA) at 8 weeks follow-up; (2) prolonged abstinence; (3) cigarettes smoked per day; (4) number of quit attempts; and (5) offer and use of nicotine replacement therapy (NRT). All outcomes were assessed at 8 weeks and 6.5 months follow-up. Design: Cluster-randomized controlled trial, with AOD service as unit of randomization, conducted January 2015–March 2016. Setting: Thirty-two eligible services (provided face-to-face client sessions to ≥ 50 clients/year) in Australia were randomized to control (usual care; n = 15) or intervention (n = 17) groups by an independent blinded biostatistician. Participants: Eligible participants (≥ 16 years, current smoker) completed surveys at the service at baseline (n = 896) and telephone follow-up surveys (conducted by blinded assessors) at 8 weeks (n = 471; 53%) and 6.5 months (n = 427; 48%). Intervention: Intervention services received an intervention to establish routine screening, assessment and delivery of smoking cessation care. Measurements: Primary outcome was biochemically verified 7-day PPA at 8-week follow-up. Secondary outcomes included verified and self-reported prolonged abstinence, self-reported 7-day PPA, cigarettes/day, quit attempts and offer and use of NRT. Intention-to-treat analyses were performed, assuming missing participants were not abstinent. Findings: At 8 weeks, the findings in verified 7-day PPA between groups [2.6 versus 1.8%, odds ratio (OR) = 1.72, 95% confidence interval (CI) = 0.5–5.7, P = 0.373] were inconclusive as to whether a difference was present. Significantly lower mean cigarettes/day were reported in the intervention group compared to the usual care group at 8 weeks [incidence rate ratio (IRR) = 0.88, 95% CI = 0.8–0.95, P = 0.001] but were similar at 6.5 months (IRR = 0.96, 95% CI = 0.9–1.02, P = 0.240) follow-up. At both follow-ups the intervention group reported higher rates of NRT use. Conclusions: Integrating smoking cessation treatment into addiction services did not significantly improve short-term abstinence from smoking.