Entrepreneur support agencies are highly important in the development of small-and medium-size businesses of entrepreneurs. There are a number of studies on support agencies, but studies on entrepreneurial performance from the perspective of a relationship marketing orientation (RMO) between support agencies and entrepreneurs are lacking. This study aimed to investigate the hypothesized relationships between the RMO of an entrepreneur support agency and the financial and nonfinancial performances of small- and medium-size entrepreneurs (SMEs). A total of 276 valid SMEs survey responses based on purposive sampling were collected and analyzed using partial least squares structural equation modeling (PLS-SEM). Findings indicate that trust and reciprocity are the significant factors to financial performance of SMEs. Meanwhile, trust, communication, empathy, and reciprocity indicate a significant positive relationship with nonfinancial performance of SMEs. To the best of the authors’ knowledge, this is the first study to provide an interesting avenue to understand the relationship between an entrepreneur support agency and entrepreneurs to work on synergistic relationship approaches in order to remain sustainable in the market. This study has also drawn specific implications for SMEs and government agencies for entrepreneur and policy planning to coordinate appropriate entrepreneurship development programs and strengthen the entrepreneurship ecosystem.