The purpose of this study is to explore changes in university students’ self-directed learning attitude through the implementation of self-assessment in a classroom setting. The current study adopted Guglielmino’s (1977) characteristics to investigate changes in students’ self-directed learning attitude over time: self-directedness, responsibility, creativity, and problem-solving. A class of 24 students enrolled in Current English Practice was observed for 15 weeks, where four self-assessment sessions were administered. After mid-term exam, a questionnaire was conducted to find out whether self-assessment helped students with their self-directed learning attitude. Additionally, in-depth interviews were conducted with four students of a group regarding possible changes in self-directed learning attitude through self-assessment in the course of time. The findings are as follows. First, the results of the survey indicated that students felt positive changes in those four characteristics of self-directed learning attitude by the implementation of self-assessment in the classroom. Second, the analysis of in-depth interviews supported the findings of the questionnaire that self-assessment provided students with opportunities to strengthen their self-directed learning attitude. However, there is a research limitation that the impact of self-assessment cannot be singled out because of the flipped learning method in class.