With globalization of sports industry, consumers came to purchase foreign sports goods and professional sportsmen also frequently made inroads to larger world stages. Sports goods companies recognized that such activities of professional sportsmen are effective in promotion of sales increase for sports goods of related event so that they use this goods promotion. That is, in order to increase sales of their goods, the companies let professional sportsmen use their clothes or golf products by paying endorsement income to professional sportsmen, or are signing a endorsement agreement to promote their brands by showing the brands on clothes or hats professional sportsmen use. Such flow happens in most of sports influenced by advertising in golf as well as soccer, tennis etc. Recently foreign professional sportsmen frequently participate in sports competitions held in other countries and they are paid by endorsement agreement made between foreign professional sportsmen and sports goods companies. As a result, this led to problem in taxation. This article dealt with a case of professional golfer Sergio Garcia who is a resident of Swiss. While Sergio Garcia acted in the United States, Sergio Garcia received endorsement income. Regarding this income, there was dispute with Internal Revenue Service in the United States. The main issues of the case are if the endorsement income is royalty income or personal service income, and if such income can be taxed in the United States. Although such case is not directly related to South Korea, there could be a possibility of same case happened in our country because recently foreign professional golfers are increasingly signing a endorsement agreement with korean companies and are paid. Accordingly, the article investigated content of judgement of the United States Tax Court related to endorsement income. And then, I examines implications, problems and improvements in the tax law of South Korea regarding to issues of endorsement income.