The purpose of this study is to examine the effect of internal marketing (IM) on competitive advantage in the organizational coaching approach to gain competitive advantage in Korea. This study is to construct the sub -elements of IM as communication, compensation, and empowerment, and to identify the relationships among IM, service innovation and competitive advantage. To accomplish the purpose of this study, we conducted a questionnaire survey of 220 employees working in three branches of the Korea Health Care Association, and collected the data and verified the hypotheses through SPSS and AMOS analysis. As a result, IM has a significant effect on service innovation positive and direct influence on competitive advantage respectively as organizational coaching. However, the relationship between IM and service innovation did not supported. In other words, there is no mediating effect of service innovation on the relationship between IM and competitive advantage. These results suggest that IM enhances competitive advantage as a role of organizational coaching. Therefore, this paper suggests practical implications for public hospital managers, including private hospital managers, from a management perspective.