This study aims to examine the relationship between internal marketing and competitive advantage in the organizational coaching approach to gain competitive advantage in Korea. We construct the sub-elements of internal marketing that are communication, compensation, and empowerment, and identify the relationships among internal marketing, 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, internal marketing has a significant positive influence on service innovation and directly affect competitive advantage as organizational coaching. However, the effect of internal marketing on service innovation did not support. In other words, there is no mediating effect of service innovation on the relationship between internal marketing and competitive advantage. These results suggest that internal marketing 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.