The purpose of this study is to investigate how Korean English learners’ self-directed learning ability varies depending on their learning style and to find out the relationship between their learning style and self-directed learning ability in asynchronous online English classes. The research was implemented for 15 weeks with 66 Korean university students. This study classified students into four learning styles of KLSI 3.1, and examined what changes were made in self-directed learning ability for each style. The results were as follows. First, all of the students with diverging, accommodating, converging, and assimilating learning styles improved their self-directed learning ability. The ranking of learning styles with high improvement in self-directed learning ability was in the order of accommodating, diverging, converging, and assimilating. Second, there was a statistically significant difference in the improvement of self-directed learning ability between diverging and accommodating, and between accommodating and assimilating. Third, among the seven factors of self-directed learning ability, four factors, Zeal for Learning, Voluntary Planning, Future Orientation, and Original Approach showed significant differences in the degree of improvement by learning styles. These findings indicate that teachers should consider learners with various learning styles to promote their self-directed learning abilities in asynchronous online English classes.