This study examines the possible benefits and effects of post-M&A integration on new product development (NPD) performance in terms of efficiency and effectiveness. The total sample size was 251 respondents. Confirmatory factor analysis (CFA) and structural equation modeling (SEM) were used for statistical analysis. The results demonstrate that external integration correlates positively with internal integration. Although external integration relates positively to new product competitive advantage (NPCA), internal integration does not have a positive correlation with NPCA. Further, product vision positively correlates with NPCA and NPD performance, and NPCA positively correlates with NPD performance. In addition, an examination of the mediation effect in terms of Sobel t-test reveals that the NPCA is a significant mediator for the influence of interdepartmental integration on NPD performance. Moreover, this study provides a framework for managing post-M&A integration and closes with a discussion of the theoretical and practical implications of the research findings.