The study investigates how the test modality (spoken or written) of classroom weekly quizzes influences vocabulary learning strategies and facilitates learning the spoken and written knowledge of form-meaning connection in L2 words. Japanese university students in academic English courses were assigned to two experimental conditions (spoken test and written test groups). The spoken test group prepared for and took weekly quizzes delivered in spoken format, whereas the written test group took the same quizzes delivered in written format. Over 10 weeks, learners were presented with the spoken or written forms of 20 English words and asked to provide the L1 translations of those words. Before and after the semester-long treatment, 45 target words were tested in both spoken and written format via L2-to-L1 translation tasks. Additionally, a questionnaire survey on vocabulary learning strategies was conducted to examine how learners prepared for weekly quizzes outside of the classroom. Results revealed that learners in the spoken test group showed a significantly larger gain in spoken vocabulary than did the learners in the written test group. However, there was no significant difference between the two groups for written vocabulary learning. The spoken test group tended to rely on studying target vocabulary in a spoken form more frequently, whereas the written test group studied vocabulary in written form more frequently. This study provided implications for how teachers should administer classroom testing with the aim to develop learners' L2 spoken vocabulary knowledge effectively.