The present study looks into a relationship between Korean middle school students’ English learning motivation and their behavior toward learning English: (1) students’ commitment to studying English and (2) the sustenance of the commitment. A total of 287 students in 4 different schools participated in the study and data were collected from the students via survey questionnaires. The collected data were analyzed through multiple regression for both the influence of students’ motivation on their commitment to English study and the influence of students’ motivation on the sustenance of their commitment. Results show that (1) students with higher motivation in learning English tend to spend more time studying English than those with lower motivation, with student’s gender, general English proficiency, the beginning age of learning English, and self-efficacy in studying English taken into account; (2) students with higher motivation sustain their commitment to English study better than those with lower motivation, accounting for the control variables.