Students' educational motivation is significant for performance and achieving learning, but little is known about what fuels such motivation. Educational motivation is regarded as the drive and inner state that energise educational activities, facilitate learning and channel behaviour towards achieving educational goals. Educational motivation paves the way for students to learn and acquire the knowledge that is essential for successful study outcomes. This article aims to explore what determines students' educational motivation. Building on the self-determination theory, we modelled the influence of teachers' leadership and students' self-efficacy on students' educational motivation. We used survey data from a sample of upper secondary school students in Sweden; we received a total of 993 answers, equal to a response rate of 74%. The results show that students' self-efficacy and teacher leadership are of extreme importance for students' educational motivation, and that highly efficacious students lose most educational motivation when the teacher's leadership is poor. The results thus support the importance of teachers' leadership for encouraging student learning.