Motivation plays an important role in foreign language learning. To investigate factors that influence motivation level, the researcher surveyed 102 students studying Japanese at the University of Washington and interviewed 10 of them. From their responses, the researcher identified four de/motivational factors: (1) teachers, (2) feedback, (3) difficulty of the class, and (4) feeling of progress. These findings also suggest that the impacts of these factors occur at different levels, take different forms, and have different strengths. The study also discusses the psychology of students underlying the influence of these de/motivational factors. Furthermore, students most frequently mentioned “teachers” and “feeling of progress,” which partially agrees with four previous related studies. Finally, the researcher briefly discusses the teachers’ perspective.