A growing body of vocabulary learning strategies (VLSs) studies focuses on accumulating empirical evidence on the relationship between frequency of VLS use and vocabulary acquisition by using the frequency-based measures of VLSs. Our study by contrast, examined which VLSs are perceived as important and useful, and how they are employed by Japanese university students learning English as a foreign language (N = 40). Further, we investigated whether university students' perceptions and use of strategies vary between higher- (n = 16) and lower-proficiency groups (n = 24). To this end, we used the KH Coder software and produced co-occurrence networks to categorize the words extracted from the results of an open-ended questionnaire. The results revealed that Japanese university students perceived cognitive strategies related to word form, sound, association learning, and metacognitive strategies as important and useful, and employed them frequently. Results from the two proficiency groups showed that while the higher-proficiency group perceived the importance of metacognitive strategies, these tendencies were not observed in the lower-proficiency group. Given the possibility that learners' proficiency influences the use of VLSs in the vocabulary learning process, considerations and suggestions for future VLSs studies and teaching are discussed.