The authors propose that the effects of multiple identities on psychological well-being depend on the number of identities, importance of those identities, and relationship between them. Specifically, this model predicts that when identities are highly important, having many versus few identities leads to greater psychological well-being if the identities are in harmony with each other-providing resources and expecting similar behaviors-but leads to lower psychological well-being if the identities conflict with each other-depleting resources and expecting incompatible behaviors. However, when identities are less important, neither the number of identities nor identity harmony should affect well-being. The authors further propose that emotions corresponding to self-perceptions of actual/ought self-discrepancies mediate these effects. Results supported this model. The authors discuss implications of this model for well-being in the context of the increasing social complexity of modern life.