Although supplier development is a mature tool to increase performance and capabilities, little is known about the impact on sustainable supplier practices and the role of buyer power use. This study investigates the relationships between buyer power, supplier development and sustainable supplier practices. We developed and tested a conceptual model with survey data from 130 managers in Dutch supplying companies. The results indicate a positive impact of direct (active involvement) and indirect (communication) supplier development on sustainable supplier practices. Furthermore, we found paths that run from coercive and non-coercive power and (direct and indirect) supplier development to the adoption of sustainable supplier practices. Apparently, companies stimulate sustainable supplier practices through supplier development, further enhanced by the use of their buying power.