The aim of this study was to determine if, and when, the neural processes involved in switching associations formed with angry and happy faces start to diverge. We measured event-related potentials (ERPs) and behavioural responses while participants performed a reversal learning task with angry and happy faces. In the task, participants were simultaneously presented with two neutral faces and learned to associate one of the faces with an emotional expression (either angry or happy), which was displayed by the face when correctly selected. After three to seven trials, the face that had consistently been displaying an emotional expression when selected would instead remain neutral, signalling the participant to switch their response and select the other face on the subsequent trial. The neural processes involved in switching associations formed with angry and happy faces diverged 375 ms after stimulus onset. Specifically, P3a amplitude was reduced and P3b latency was delayed when participants were cued to switch associations formed with angry expressions compared to happy expressions. This difference was also evident in later behavioural responses, which showed that it was more difficult to switch associations made with angry expressions than happy expressions. These findings may reflect an adaptive mechanism that facilitates the maintenance of our memory of threatening individuals by associating them with their potential threat.