Social category conjunction is a form of multiple categorization involving the combination of two simultaneously salient constituent categories to form a complex category (e.g., female soldier). Research has reliably demonstrated that perceivers often apply emergent traits when forming impressions of novel incongruent social category conjunctions, that is, traits not associated with the simple constituent categories (e.g., Kunda, Miller, & Claire, 1990). However, the theoretical literature modeling the mechanisms underlying impression formation in novel social category conjunctions is less well established and inconsistent. In this article, we critically evaluate the current state of empirical research and theory on novel social category conjunction, with particular reference to emergent traits, aiming to provide a more coherent framework for future research and theory. In addition, we seek to emphasize the wider importance of emergent traits, by drawing out links between research and theory on social category conjunctions with broader perspectives of impression formation.