The aim of this paper is to explore the relationship between the L1 semantic information and the L2 semantic restructuring of Japanese EFL learners. According to Semantic Transfer Hypothesis (Jiang, 2000), learners are required to modify and elaborate the meaning associated with the learned foreign language words. It is also claimed that L1 transferred semantic information should have a crucial role in the progress of L2 semantic restructuring. In this study, English word pairs sharing the same L1 translation equivalent were presented to 128 Japanese EFL learners in the sentence completion task. The results showed that (1) most of the L2 words are more appropriately chosen than the random rate score 33%, and (2) L1 word familiarity has the highest correlation with the scores among the other L1/L2 frequency and L2 word familiarity. These results were interpreted as evidence for the necessity of the vocabulary instruction in the EFL environment and the important role of the transferred L1 meaning for fostering the L2 semantic restructuring in FL vocabulary acquisition.