This study analyzes the impact of horizontal and vertical communications on researchers' creativity, knowledge sharing, group cohesion, and Research and Development(R&D) performance within the context of national R&D programs. Survey is conducted with 112 researchers who have participated in national R&D projects and PLS-SEM is utilized to examine the research model investigating relationships between communications and performance. Results show that horizontal communications have a positive impact on group cohesion; vertical communications have a positive effect on individual creativity, knowledge sharing, and group cohesion; individual creativity and group cohesion have a positive effect on R&D performance; and vertical communications affect R&D performance through individual creativity and group cohesion. Some results do not support previous literature: horizontal communications and knowledge sharing are shown not to impact R&D performance. The difference in results could be attributed to the demographic characteristics of the respondents that most of them are working for public institutions; lack of R&D researching manpower, and inadequate sharing platform. This study supportsthe importance and necessity of internal communications among researchers to drive innovative R&D performance in national R&D programs. The findings also provide managerial implications for national R&D program’s successful execution.