This study investigates the relationship between depth and breadth of vocabulary knowledge and EFL learners' listening comprehension. It is designed to find out whether there is a meaningful relationship between vocabulary knowledge and listening comprehension in general, and to determine which dimension of vocabulary knowledge is a better predictor of successful listening comprehension in particular. Data gathered through three tests including Vocabulary Knowledge Test (VLT), Word Associate Test (WAT), and standardized listening comprehension test, from 32 EFL learners were analyzed and the findings revealed that there is a high and positive relationship among the three variables and also between the independent variables. Future analysis indicated that though both VLT and WAT contribute to listening comprehension, VLT is a better predictor of successful listening comprehension performance.