Research has demonstrated reduced emotional reactivity in a second- (L2) compared to a first language (L1). One explanation for this states that L2 use is more cognitively demanding and thus leaves fewer resources available for emotion processing. Here, we specifically investigated this notion of differences in cognitive load during L1 and L2 use. EEG was used to investigate mismatch negativity during an auditory oddball paradigm. Native Swedish speakers with L2 English were asked to read text excerpts in their L1 and L2, whilst simultaneously listening to standard and deviant auditory tones to be ignored. The results showed significant oddball effects (i.e., mismatch negativity) in L1 but not in L2. Together with a lower accuracy in the L2 condition, these results imply a higher cognitive load during L2 reading. These findings are explained within a resource allocation framework and are suggested as a possible explanation of the underlying mechanisms of the foreign language effect. © The Author(s) 2026.