The present study examined the interaction effects between teachers' choice of language in lexical explanation and second language (L2) learners' proficiency level on the learning of phrasal verbs and listening comprehension in a meaning-focused listening activity. Undergraduate L2 learners with two different levels of proficiency (intermediate and advanced) were assigned to three different conditions. These conditions included (1) code-switching, in which teachers briefly switched to learners' first language for vocabulary teaching purposes, (2) L2-only, in which teachers maintained L2 for overall instruction and vocabulary teaching, and (3) control condition, in which learners were not given instruction about target vocabulary. The results revealed that teachers' instruction about target vocabulary brought about more gains in learning of phrasal verbs than lack thereof. In addition, teachers' use of code-switching benefited intermediate-level learners most, who were able to gain similar levels of vocabulary learning and listening comprehension to advanced learners.