Successful smoking cessation appears to be facilitated by identity change, that is, when quitting or nonsmoking becomes part of smokers' and ex-smokers' self-concepts. The current longitudinal study is the first to examine how identity changes over time among smokers and ex-smokers and whether this can be predicted by socioeconomic status (SES) and psychosocial factors (i.e., attitude, perceived health damage, social norms, stigma, acceptance, self-evaluative emotions, health worries, expected social support). We examined identification with smoking (i.e., smoker self-identity) and quitting (i.e., quitter self-identity) among a large sample of smokers (n = 742) and ex-smokers (n = 201) in a cohort study with yearly measurements between 2009 and 2014. Latent growth curve modeling was used as an advanced statistical technique. As hypothesized, smokers perceived themselves more as smokers and less as quitters than do ex-smokers, and identification with smoking increased over time among smokers and decreased among ex-smokers. Furthermore, psychosocial factors predicted baseline identity and identity development. Socioeconomic status (SES) was particularly important. Specifically, lower SES smokers and lower SES ex-smokers identified more strongly with smoking, and smoker and quitter identities were more resistant to change among lower SES groups. Moreover, stronger proquitting social norms were associated with increasing quitter identities over time among smokers and ex-smokers and with decreasing smoker identities among ex-smokers. Predictors of identity differed between smokers and ex-smokers. Results suggest that SES and proquitting social norms should be taken into account when developing ways to facilitate identity change and, thereby, successful smoking cessation.