The purposes of this study were to develop the instructional model for enhancing self-directed learning skills of Bangkok University students, study the impacts of the model on their English reading comprehension and self-directed learning ability as well as explore their opinion towards self-directed learning. The model development process consisted of a review of literature, the design of the learning model, and evaluation of its effectiveness by experts' validation and implementation of the model in the classroom. The research instruments included 1) the Honey and Mumford's Learning Style Questionnaire used to divide the students into four groups: activist, reflector, theorist, and pragmatist, 2) self-directed learning readiness scale created by Guglielmino, 3) a reading comprehension test, and 4) an opinion questionnaire towards self-directed learning. Over 12 weeks, the designed Self-directed Learning Instructional Model was employed with 120 students enrolled in Fundamental English I course in the first semester of 2010 academic year. Then the data were analyzed by mean, standard deviation, t-test, and One-way Analysis of Variance. Regarding the effectiveness of instructional model, the experts accepted that the model was appropriate. From implementing the model in class, it was found that the English reading proficiency mean scores of the post-test of students in four learning styles were significantly higher than those of the pre-test (p less than 0.05). Moreover, the post-test mean scores of self-directed learning ability of students in four learning styles were significantly higher than the pre-test mean scores (p less than 0.05). The students had a high level of opinion towards self-directed learning. The findings suggest that self-directed learning environment be provided for students to enhance their reading skill and self-directed learning ability. (Contains 10 tables.)