This study explored the longitudinal changes of Japanese EFL learners' psychological attributes of unwillingness to speak English in a task-based classroom. Thirty-three university students participated in this study. They engaged in a communicative task once a week for two semesters. They completed a questionnaire examining the psychological attributes of their task performance. The results suggest that overall task-based communicative lessons were effective in reducing unwillingness-related psychological attributes. The following qualitative analysis revealed that the learners became aware of the gap between their perceived and actual L2 skills, which reduced some learners' confidence. Additionally, the results indicated that personality, such as introversion, low-cooperativeness, or lack of sociability affected the extent to which unwillingness-related attributes were impacted. The paper concludes with a discussion of the positive effects of task-based lessons on Japanese EFL learners' unwillingness to speak English, and the possible latent variables which weaken the effectiveness of these lessons.