Background: Emerging adulthood presents unique challenges to smoking cessation that are not well understood. During this phase, smoking identities can develop that become obstacles for quitting, particularly in social situations where smoking is accepted and expected. Using a social identity approach, this study explores how social relationships and normative group behaviours can be barriers to transitioning from a smoker to non-smoker identity. Method: Six focus groups of five participants (N = 30) were conducted with participants aged 18-25 years (57% male). Participants’ smoking status was ascertained to construct six groups, two each of daily smokers, occasional (non-daily) smokers, and ex-smokers. Results: Salient in-group identities invoked out-group comparisons that could create barriers to change including feeling conflicted about becoming a “non-smoker”, and maintenance of pro-smoking group norms. Three subthemes were identified: 1) Managing the division between smoker and non-smoker groups; 2) The isolation associated with navigating others’ expectations about quitting when attempting to quit; and 3) Encountering normative in-group smoking-related behaviours when attempting to quit. Conclusions: The transition from smoker to non-smoker, when understood from a social identity approach, is not straightforward. Identifying as a smoker can invoke negative judgements from non-smokers while, conversely, attempting to quit may lead to perceived rejection among smokers. Further research is needed to explore whether perceptions of social risk can be reduced by increasing the salience of a transitional “quitter” identity that helps to reduce the perceived gap between “smoker” and “non-smoker”.