The present study uses event-related potentials (ERPs) to investigate lexicosemantic prediction in native speakers (L1) of English and advanced second language (L2) learners of English with Swedish as their L1. The main goal of the study was to examine whether learners recruit predictive mechanisms to the same extent as L1 speakers when a change in the linguistic environment renders prediction a useful strategy to pursue. The study, which uses a relatedness proportion paradigm adapted from Lau et al. (2013), focuses on the N400, an ERP component that is sensitive to the ease of lexical access/retrieval, including lexical prediction. Participants read 800 prime–target pairs, presented word by word and divided into two blocks, while they searched for animal words. Unknown to them, some of the pairs were semantically associated, which is known to reduce the amplitude of the N400 via spreading semantic activation. Most importantly, the proportion of semantically related pairs increased in the second experimental block (via fillers), thereby increasing the reliability of the primes as predictive cues and encouraging prediction. Results from 36 L1-English speakers and 53 L2 learners showed an N400 reduction for related (remain-stay) relative to unrelated targets (silver-stay) across blocks. Crucially, this N400 reduction for related targets was significantly larger in the block that encouraged prediction, in both L1 and L2 speakers, consistent with the possibility that both groups recruited similar predictive mechanisms when the context encouraged prediction. These results suggest that, at high levels of proficiency, L2 speakers engage similar predictive strategies to L1 speakers.