Supplier involvement (SI) for new product development (NPD) entails multiple relationships between buyers and their suppliers, demanding appropriate coordination mechanisms for successful NPD collaboration. This study proposes that supplier salesperson behaviors act as coordination mechanisms in the SI setting for NPD information regulating and process regulating behaviors. Drawing on information processing theory and using survey data matched with archival data, this study unravels the role of supplier salesperson behaviors in the relationship between the timing of SI and supplier performance, which is the precursor to the buyer’s NPD performance. Our results indicate that although information regulating behaviors positively moderate the timing of SI–supplier performance linkage, process regulating behaviors weaken this linkage across multiple NPD stages. This study contributes to the literature by highlighting a new salesperson’s role in the SI setting (i.e., salesperson as coordinator), which has been previously overlooked.