The transition from secondary to higher education is a challenging process, in which the development of students' motivation plays a pivotal role. The current study examines whether self-efficacy--and how it develops--is able to explain the growth in motivation. The current longitudinal study included five waves, across a period of 25 months (i.e. start of the final year of secondary education until the beginning of the second year of higher education). Results show--contrary to our hypothesis based on the self-determination theory and social cognitive theory--that the growth in autonomous motivation positively predicts the growth in self-efficacy and that this 'reversed' model is superior in terms of fit and explained variance to the hypothesised model.