Aim To evaluate the efficacy of nortriptyline ( NOR) added to a multi-component smoking cessation intervention, which included cognitive-behavioural therapy ( CBT) and provision of nicotine replacement therapy ( NRT). Design Randomized controlled trial ( RCT) comparing two study groups with blinded follow-up at 3, 6 and 12 months. Both groups received a multi-component smoking cessation intervention comprising two half-hour individual sessions of CBT and NRT with either active NOR or placebo. Setting Prisons in New South Wales (17) and Queensland (one), Australia. Participants A total of 425 male prisoners met inclusion criteria and were allocated to either treatment ( n = 206) or control group ( n = 219). Measurements Primary end-points at 3, 6 and 12 months were continuous abstinence, point prevalence abstinence and reporting a 50% reduction in smoking. Smoking status was confirmed by expired carbon monoxide, using a cut-point of ≤10 parts per million. Findings Participants' demographics and baseline tobacco use were similar in treatment and control groups. Based on an intention-to-treat analysis, continuous abstinence between the treatment and control groups was not significantly different at 3 months (23.8 versus 16.4%), 6 months (17.5 versus 12.3%) and 12 months (11.7 versus 11.9%). Conclusion Adding nortriptyline to a smoking cessation treatment package consisting of behavioural support and nicotine replacement therapy does not appear to improve long-term abstinence rates in male prisoners.