Through their teaching behaviours, physical education teachers play an important role in promoting physically active lifestyles among their students by shaping their experiences of physical activity. As described in previous chapters, the teaching behaviours adopted by teachers can affect students’ behaviours, motivation for physical education and physical activity - effects that can last from childhood to adulthood - as well as their psychological needs satisfaction and frustration. While a significant number of studies has examined the consequences of these behaviours and highlighted their importance, less attention has been paid to identifying the antecedents of physical education teachers’ need-supportive and need-thwarting behaviours, as conceptualised in self-determination theory. The purpose of this chapter is to present the proximal and distal antecedents of these two types of teaching behaviours that have been examined in studies conducted in physical education setting and to better understand how these antecedents are interconnected and related to need-supportive and/or need-thwarting behaviours. A deeper understanding of why teachers adopt certain behaviours could help researchers and stakeholders to focus on these antecedents to develop and implement science-based and/or evidence-based professional development programs. The ultime goal is to encourage more need-supportive and fewer need-thwarting teaching behaviours thereby fostering greater student engagement in physical education and physical activity.