In a working environment that is high-risk, knowledge-intensive, extremely stressful, and competitive, medical institutions have increasingly come to value the concepts of social capital and health promotion. In this study conducted at hospitals in Taiwan, we explored the relationships among social capital (institutional trust and interpersonal trust), health promotion, and job satisfaction. We found that institutional trust had a significantly positive effect on both interpersonal trust and health promotion. In addition, institutional trust, interpersonal trust, and health promotion had significantly positive effects on job satisfaction. Furthermore, in descending order, institutional trust, health promotion, and interpersonal trust, all substantially affected job satisfaction. Therefore, we concluded that Taiwanese hospitals should reinforce both social capital, and health promotion programs to improve job satisfaction.