The purpose of this study is to analyze a mechanism whereby social support (instrumental and emotional support) at the workplaces of knowledge workers nurtures positive feelings and influences the performance of both organizations and individuals. A survey questionnaire was administered to a total of 143 nurses and care workers who work in a hospital. The following two findings were revealed through the results of the quantitative survey study: First, instrumental support had a positive influence on both job satisfaction and organizational commitment, and emotional support had a positive influence on organizational commitment. Second, the relationship between social support and turnovers was mediated by job satisfaction or organizational commitment. These results suggest that social support is an effective means of positively influencing the performance of knowledge workers.