The study explored factors explaining changes in a deep approach to learning. The data consisted of interviews with 12 students from four Bachelor-level courses representing different disciplines. We analysed and compared descriptions of students whose deep approach either increased, decreased or remained relatively unchanged during their courses. We also explored the effect of the teaching-learning environment on these changes. Individual factors (such as investing time and effort in studying regularly during the courses, the goals set for the courses, study skills and skills in regulating one's own learning) most clearly explained the changes in one's deep approach, while students' experiences of the teaching-learning environment and how they perceived the quality of teaching provided no clear explanation of the changes. An exception was the way in which students experienced the challenges presented by the courses, which was more clearly related to the deep-approach changes.