This study investigated two prominent issues in the comprehension of language switches. First, how does language switching direction affect switch costs in sentence context? Second, are switch costs modulated by L2 proficiency and cross-linguistic activation? We conducted a self-paced reading task involving sentences that switched between participants’ L1 Dutch and L2 English. The cognate status of the main verb was manipulated to examine the influence of co-activation on intra-sentential switch costs. The reading times indicated the influence of switch direction: a cost was observed for switches into L2 but not for switches into L1, and the magnitude of the costs was correlated with L2 proficiency, indicating that switch costs in language comprehension depend on language dominance. Verb cognates did not yield a cognate facilitation effect nor did they influence the magnitude of switch costs in either direction. The results are interpreted in terms of an activation account explaining lexical comprehension based on L2 proficiency.