Empirical evidence has attested to the benefits of autonomy support in a classroom context, in facilitating students' autonomous motivation, well-being, creativity, engagement, and persistence. However, most interventional research aiming to increase teachers' autonomy-supportive behaviors has been conducted in school and college contexts, with few studies aimed at university tutors. The current study implemented a brief theory-driven autonomy-supportive intervention in university seminars and developed an observational checklist instrument to assess behavior change. Tutors who received brief training in autonomy-supportive teaching techniques showed significant increases from baseline in two important autonomy-supportive behaviors in their classes. Potential implications and suggestions for further development of the intervention are discussed. (Contains 3 tables and 2 figures.)