Research on reading development has shown that reading large amounts of text leads to improved reading comprehension. The first and probably most important step is to motivate students to read more; however, there has been little research on the relationship between reading amount and motivation for L2 reading. Thus, the current study aims to explore what constitutes Korean EFL university students’ motivation for reading in English through extensive reading and to further investigate the factors that influence Korean EFL university students’ motivation to read more. A quasiexperimental research design was used, implementing extensive reading in two intact classes of eighty-three students over a 15-week semester. A 4-point Likert scale extensive reading motivation questionnaire was developed and administered to the students at the end of the semester. A factor analysis was used to evaluate the underlying structure of motivation for extensive reading in English. Results generated three factors: L2 reading for academic and future career success, L2 reading for enjoyment, and L2 reading avoidance. To determine which factors would predict reading amount, multiple regression analysis was computed. Results indicated that one predictor variable, L2 reading for academic and future career success, was able to predict the students’ motivation for reading.