The recall rates of various products these years have triggered a new round of interests in the impacts of supplier involvement (SI) and customer involvement (CI) on new product performance (NPP). However, existing literature looks at either SI or CI but not both. Most supply chain management papers focus on SI and NPP while research in marketing field focuses on CI and NPP. Additionally, the NPP has not been elaborated into detail dimensions in these previous studies. This research investigates the impact of both SI and CI on the three dimensions of NPP, namely new product quality and reliability, time to market and product innovativeness. The research was based on the data from over 600 manufacturers in 21 countries. Structural equation modeling (SEM) is used to test the simultaneous impact of SI and CI on NPP. The results show that SI influences all the three dimensions of NPP while CI influences quality and reliability. The research also reveals that companies pay more attention to CI than SI. It seems that more efforts in both academic and practical fields are needed to enhance SI in relation to NPD. The research suggests that both SI and CI should be implemented in new product development process. It is not a two-party issue but a three-party-issue.