The study explores how native language (L1) lexical access is affected by immersion in a second-language (L2) environment, and by short-term reimmersion in the L1 environment. We compared the L1 picture-naming performance of Polish–English bilinguals living in the UK (migrants) against that of bilinguals living in Poland (controls). Each group was tested twice: the migrants while in the UK (L2 immersion) and after visiting Poland (L1 reimmersion); the controls twice in their L1 environment. Contrary to our expectations, there was no main effect of group, thus suggesting that L2 immersion per se does not impact L1 lexical access. Nevertheless, migrants benefitted from L1 reimmersion by showing faster naming latencies for high-frequency words after a short visit to their home country, probably due to more opportunities to encounter these words. Overall, the study shows that the cognitive system is sensitive to the language environment by quickly adapting the activation level of lexical items.