Purpose - In the development of new products, suppliers involvement and developing products jointly can be said to be strategic activities that utilize the lack of knowledge from external organizations. In this new product development, supplier involvement has been proven to have a positive impact on new product development performance for a long time by previous research. However, sufficient academic research has not been conducted on the influence of supplier involvement in various product strategies or sales strategies that buyers make in order to secure a competitive advantage in the market. This study argues that product strategy and sales strategy used by buyers in the development of new products will control the effect of supplier involvement on new product development performance in order to compensate the lack of these academic aspects. Research design, data, and methodology – Specifically, we selected the modularization strategy of the product as the product strategy, which is considered as an important strategy in the new product development through the preceding research, and the mass customer satisfaction strategy was chosen as the sales strategy. In order to achieve these research objectives, regression analysis was conducted using data from manufacturing productivity panel collected jointly by the Ministry of Industry, Trade and Industry and the Korea Productivity Center. Results - As a result, supplier involvement and new product development performances (development cost efficiency, customer satisfaction) were positively related. The product modularity strategy proved to have an interactive effect on the relationship between supplier involvement and new product development performances (development cost efficiency, customer satisfaction). However, it has not been confirmed that there is a statistically significant interaction effect between supplier involvement and new product development performances. Conclusions - Supplier involvement has positive relationships with NPD performance. In addition, product modularity strategies have interaction effects with supplier involvement and affect new product development performance (development cost efficiency and customer satisfaction). The results of this study are of academic significance in the case of lack of empirical studies on the effect of supplier participation on the effect of buyer 's strategy when a supplier participates and develops new products jointly.