ABSTRACT This paper investigates the relationship between language learning strategies and L2 proficiency. Language learning strategies were measured by the Strategy Inventory for Language Learning (SILL, ESL/EFL Student Version), and L2 proficiency was determined by the Test of English as a Foreign Language (TOEFL) for 332 university students learning English in Korea. The findings of this study are: (1) the relationship between language learning strategies and L2 proficiency was linear; (2) all six categories of language learning strategies as well as total language learning strategies were significantly correlated with the TOEFL scores; and (3) cognitive and social strategies were more predictive of the TOEFL scores than the other four strategy categories, jointly accounting for 13 percent of the total variation in the TOEFL scores. These findings provide evidence that L2 learners need language learning strategies, specifically cognitive and social strategies in the Korean context, to facilitate L2 acquisition and suggest that language learning strategies be taught in classrooms, focusing on effective strategies that may improve the results of strategy training.