Individual differences in second language (L2) learning can offer insights into the neurobiological bases of learning aptitude. One neurophysiological marker of inter-individual differences in cognition is the individual alpha frequency (IAF), a trait-like measure correlated with cognition. Further, the N400 is an electrophysiological marker indexing stimulus irregularity and has been used to study L2 learning; however, its relationship with IAF and L2 learning remains unknown. To examine the relation between IAF and L2 learning (indexed by N400 amplitude), we report data from a modified miniature language learning study. After a vocabulary learning period, participants (N = 38, Mage = 25.3, SD = 7.13) judged the grammaticality of classifier-noun pairs, with mixed-effects modelling revealing lower IAF individuals were better than higher IAF individuals at grammaticality judgements. N400 amplitude also reduced across the experiment in low relative to high IAF individuals, indicating the relationship between IAF and language learning is more complex than initially postulated.