Learning a second language influences speakers’ first language, but there is great variability in the degree of influence that speakers exhibit. We show that some of this variability is due to individual differences in inhibitory skill. Particularly, we propose that poorer inhibitory skill leads to greater activation of competing items from the language not in use, and that this greater co-activation ultimately leads to greater influence of the co-activated items on one another. Specifically, we show that bilinguals with lower inhibitory skill exhibit greater influence of the second language on the first. Late English–French bilinguals residing in France produced and perceived Voice Onset Time of voiceless stops in English in a more French-like manner, the lower their inhibitory skill was. We discuss the implications of these results for the role of inhibitory skill in shaping representation in bilingual as well as monolingual language processing.