This study examined the effectiveness of explicit instruction of vocabulary learning strategies (VLSs) over a 10-week semester with a group of 146 female EFL learners from two Japanese universities. A vocabulary test and questionnaires on VLSs and motivation were administered at the beginning of the course. The learners were divided into two groups based on the vocabulary test results: an experimental group and a control group. Only the experimental group received explicit instruction on VLSs in combination with their regular language lessons. The same instruments were re-administered at the end of the course to examine the changes in both the questionnaire responses and test scores. Qualitative analyses were also conducted to explore the findings in detail. The results show that the experimental group outperformed the control group in the vocabulary test. It was also found that (1) strategy training was effective for both changing the repertoire of strategies used and improving their frequency of use, (2) the training increased the use of certain strategies more than it did for other strategies, and (3) different types of learners exhibited different responses to the strategy instruction. This study's findings contribute to a better understanding of strategy instruction in general and VLSs in particular. (Contains 3 figures, 5 tables and 5 notes.)