This randomised controlled trial tests whether teachers can be trained to become more autonomy-supportive — and whether the key mechanism is their capacity for perspective-taking, specifically the ability to see classroom experience through their students’ eyes. The study found that professional development focused on perspective-taking produced measurable shifts in teaching behaviour, with teachers providing more choice, acknowledging student feelings, and offering meaningful rationales. These changes in turn predicted improvements in student motivation and engagement. The findings have direct practical implications: autonomy support is not a fixed personality trait but a teachable skill, and the path to it begins with how teachers understand their students’ inner lives.