Summary of findings
In this qualitative study, we investigated participants' subjective experiences of mechanisms underlying change in smoking behaviour. Participants reported that the integrated smoking cessation and mood intervention helped facilitate reductions in smoking through increased self‐awareness of smoking patterns, and supported them in developing individualized behavioural and cognitive strategies to aid cessation. Participants stated that the regularity of support, the supportive, ‘non‐lecture‐y’ therapeutic style of IAPT practitioners and being offered the smoking intervention at the ‘right time’ (i.e., integrated with mental health support) all contributed to participants' sense of being able to make changes to the smoking. These findings further our understanding of the active ingredients and processes for behaviour change in this integrated intervention.