There is ample evidence showing that listeners are able to quickly adapt their phoneme classes to ambiguous sounds using a process called lexically-guided perceptual learning. This paper presents the first attempt to examine the neural correlates underlying this process. Specifically, we compared the brain’s responses to ambiguous [f/s] sounds in Dutch non-native listeners of English (N=36) before and after exposure to the ambiguous sound to induce learning, using Event-Related Potentials (ERPs). We identified a group of participants who showed lexically-guided perceptual learning in their phonetic categorization behavior as observed by a significant difference in /s/ responses between pretest and posttest and a group who did not. Moreover, we observed differences in mean ERP amplitude to ambiguous phonemes at pretest and posttest, shown by a reliable reduction in amplitude of a positivity over medial central channels from 250 to 550 ms. However, we observed no significant correlation between the size of behavioral and neural pre/posttest effects. Possibly, the observed behavioral and ERP differences between pretest and posttest link to different aspects of the sound classification task. In follow-up research, these differences will be further investigated by assessing their relationship to neural responses to the ambiguous sounds in the exposure phase.