With research showing the benefits of self-directed learning, more activities are needed to provide learners opportunities for self-directed practice (Khomson, 1997; Lee, 1998; Phongnapharuk, 2007). A 12-week experimental study was performed with 80 EFL learners; one group contained 40 Communication Arts students and the other one consisted of 40 Business Administration students. All of them were taught through self-directed learning activities for twelve weeks. The instruments used in this study included an English proficiency test, a self-directed learning questionnaire, a learning style questionnaire, and an opinion questionnaire toward self-directed learning activities. The data were analyzed by One-way ANOVA, dependent and independent t-tests, mean and standard deviation. Results from the statistical tests revealed that students in both groups gained higher English mean scores and self-directed learning abilities at a significance level even with limited time spent practicing language skills in a self-directed environment. When dividing BA and CA students into four learning styles, it was found that language mean scores of students in all the four groups improved significantly; however, only two groups of BA students, namely pragmatists and theorists, improved their self-directed learning ability.