Management style is treated in a variety of ways across the training and development literature. Yet few studies have tested the training-based malleability of management style in a for-profit, authentic work context. The present research tested whether or not training intervention would help managers adopt a more autonomy-supportive motivating style toward employees and whether or not the employees of these managers would, in turn, show greater autonomous motivation and workplace engagement. Using an intervention-based experimental design, 25 managers from a Fortune 500 company received training consistent with self-determination theory on how to support the autonomy of the 169 employees they supervised. Five weeks after the managers in the experimental group participated in the training, they displayed a significantly more autonomy-supportive managerial style than did nontrained managers in a control group. Further, the employees they supervised showed, 5 weeks later, significantly more autonomous motivation and greater workplace engagement than did employees supervised by control-group managers. We discuss the malleability of managers' motivating styles, the benefits to employees when managers become more autonomy supportive, and recommendations for future training interventions and research.