This article analyzes the impact of retailer buyer power on a supplier's incentive to conduct innovation, with a focus on the supplier's investment in product variety and quality improvement. The analysis shows that an increase in buyer power, manifested through either a weakening of the supplier's bargaining position or a strengthening of a large retailer's bargaining power, leads to greater product variety and higher quality if the elasticity of demand is not too large. Increased buyer power, manifested through a strengthening of a large retailer's bargaining position, stimulates the supplier to invest more in quality improvement.