The purpose of the study is two-fold: (a) to investigate L2 learners’ receptive and productive collocational knowledge concerning the learners’ lexical proficiency levels, and (b) to explore the degree of their productive collocational knowledge. A total of 358 Korean university students participated in this study and completed a Vocabulary Size Test, two receptive collocation tests, and one productive collocation test. The results revealed that there was significance among the scores of three collocation tests. It is also observed that receptive and productive collocational competence tends to increase as L2 learners’ vocabulary size develops. Regarding productive collocational knowledge gains, significant differences were found among collocation combinations but no interaction effect was found between combination types and vocabulary levels. The findings indicated that L2 learners need to be aware of the importance of learning collocational knowledge while teachers need to attempt to help them notice high-frequency collocations that regularly occur in various contexts.