The present study investigates whether productive classroom discourse in the form of instructional and motivational classroom discourse (Turner et al., "Journal of Educational Psychology" 94: 88-106, 2002) provides a supportive social context for students that fosters the fulfilment of the basic psychological needs of autonomy and competence (Meyer and Turner, "Educational Psychologist" 37(1): 17-25, 2002; Ryan and Deci, "Contemporary Educational Psychology" 25(1): 54-67, 2000). In order to explore this, we studied the ways in which a teacher professional development programme (Dialogic Video Cycle; Gröschner et al. 2015) might affect the quality of teachers' instructional and motivational discourse. The programme provided video-based professional development on productive classroom discourse for an entire school year. During the same period of time, we explored changes in students' perceptions of autonomy and competence support and possible implications for students' intrinsic learning motivation. The study followed a two-group field-experiment design; 10 STEM classes participated (N = 226 students). The intervention group (IG) was compared to a control group (CG), which participated in traditional professional development on classroom discourse (IG: n[subscript Students] = 136, n[subscript Teachers] = 6; CG: n[subscript Students] = 90, n[subscript Teachers] = 4). The results show significant group differences in the development of instructional and motivational discourse throughout the school year, resulting in significant benefits for the IG. Furthermore, the students experienced their teachers as more autonomy- and competence-supportive throughout the year, leading to increased experiences of self-determination and intrinsic learning motivation. The results are discussed in the light of recent research and theory.