Although cross-functional integration is important for research and development (R&D), research about implications of cross-functional integration has been rather sparse. In new product development (NPD), no study to date has examined intrafirm as well as interfirm integration of key functions such as intrafirm R&D–marketing–production together with interfirm integration of host R&D–partner R&D. Such marketing and operations interface contributes to a better understanding of how operational and marketing activities impact on competitiveness and firm performance. This study collected data from 202 electronics manufacturing firms operating in an emerging economy, mainland China and Hong Kong with international R&D partnerships. The findings indicate that a high level of R&D integration between firms improved NPD performance when cross-functional integration is based on existing rather than new product configurations and key technologies. Interestingly, in high distance situations, cross-functional integration in the production validation stage generated NPD success. The findings show that high environmental uncertainties lead to a high level of host and partner firms R&D integration. However, product newness has no significant effects on R&D integration in any of the NPD stages.