In addition to being a conduit for acquiring resources, the internal and external relationship capital, accumulated from employees and partners, can be seen as the dynamic assets for building market innovation capability. This study attempts to examine the effect of relationship capital on market innovation capability and investigates how the internal relationship capital can moderate the relationship between external relationship capital and market innovation capability. The authors test the hypotheses based on a mail survey targeting the top 500 manufacturing and service industries in Taiwan. The results support the hypotheses, which posit that internal and external relationship capital is positively related to market innovation capability. Moreover, the findings also support the authors' argument that the effect of external relationship capital on market innovation capability is strengthened by internal relationship capital. The authors also discuss theoretical and managerial implications of their findings, as well as suggestions for future research.