This study aims to explore the relative importance of vocabulary and grammar knowledge in explaining success of L2 learners’ listening comprehension. 40 Chinese learners of English who were studying in a UK university participated in the study. L2 learners’ vocabulary knowledge was measured through a receptive aural vocabulary test and their grammar knowledge was measured through an aural grammar test. The Cambridge Preliminary English Test (PET) listening section was adopted to measure L2 learners’ listening comprehension proficiency. Results from correlation analysis showed that both vocabulary and grammar measures correlated with L2 listening (r = .69 and r = .75 respectively). Hierarchical regression analyses showed that both measured jointly explained 72.2% of the variance in the listening score and that each measure had its unique contributions to L2 listening. It was also found that the grammar measure explained more of the variance in L2 listening than the vocabulary measure. These results demonstrated the importance of possessing L2 vocabulary and grammar knowledge in benefiting learners’ listening comprehension.