Two studies examined whether social identity processes, i.e. group identification and social identity threat, amplify the degree to which people attend to social category information in early perception [assessed with event-related brain potentials (ERPs)]. Participants were presented with faces of Muslims and non-Muslims in an evaluative priming task while ERPs were measured and implicit evaluative bias was assessed. Study 1 revealed that non-Muslims showed stronger differentiation between ingroup and outgroup faces in both early (N200) and later processing stages (implicit evaluations) when they identified more strongly with their ethnic group. Moreover, identification effects on implicit bias were mediated by intergroup differentiation in the N200. In Study 2, social identity threat (vs control) was manipulated among Muslims. Results revealed that high social identity threat resulted in stronger differentiation of Muslims from non-Muslims in early (N200) and late (implicit evaluations) processing stages, with N200 effects again predicting implicit bias. Combined, these studies reveal how seemingly bottom-up early social categorization processes are affected by individual and contextual variables that affect the meaning of social identity. Implications of these results for the social identity perspective as well as social cognitive theories of person perception are discussed.