The implicit association test (IAT) has been widely used in social cognitive research over the past decade. Controversies have arisen over what cognitive processes are being tapped into using this task. While most models use behavioral (RT) results to support their claims, little research has examined neurocognitive correlates of these behavioral measures. The present study measured event-related brain potentials (ERPs) of participants while completing a gay-straight IAT in order to further understand the processes involved in a typical group bias IAT. Results indicated significantly smaller N400 amplitudes and significantly larger LPP amplitudes for compatible trials than for incompatible trials, suggesting that both the semantic and emotional congruence of stimuli paired together in an IAT trial contribute to the typical RT differences found, while no differences were present for earlier ERP components including the N2. These findings are discussed with respect to early and late processing in group bias IATs.