Electronic cigarettes (ECs) are an efficacious support for some but not all people wishing to stop using tobacco. While advice and practical support have been identified as increasing quit success, little research has explored the role of changes in smoking and EC-related social identities. A prospective study following 573 people attempting to quit smoking with EC support. Self-report measures of identification with being a smoker, non-smoker, vaper and dual user (people using ECs and tobacco products) were taken prior to the quit attempt and at a 12-week follow-up. Baseline identifications with being a smoker, non-smoker or dual user were not associated with smoking outcomes. Baseline vaper identity baseline was linked to more frequent tobacco abstinence at follow-up and lower levels of cigarette smoking. Levels of social identification at follow-up were consistently linked with outcomes, with vaper identity and non-smoking identities being protective and dual user identity being related to lower abstinence rates but decreased tobacco usage. Changes in identity over time were the most consistent predictor of outcomes. Findings have implications for smoking cessation practice, informing how and when identity-based interventions may be effective and our understanding of how identity transitions occur.