The market structure of the Pharmaceutical Industry, which has an extremely important both socially and economically position, is carefully monitored by regulatory authorities. The consantration of pharmaceutical companies tends to adversely affect consumer welfare as well as resource distribution in the economy. The competitive structure of the markets is determined by the concentration indices. For these reasons, in this study the market concentration ratios of the pharmaceutical sector in Turkey are calculated by using concentration measures such as Concentration Ratio; Herfindahl-Hirschman; Hall-Tideman; Rosenbluth; Comprehensive Industrial Concentration; Hannah-Kay; Hause and the Entropy measure with the annual sales revenue data of the companies in the sector for the 2009-2016 period.According to the results, pharmaceutical sector in Turkey has a low concentrated market structure. In addition, the Rosenbluth index presents the most consistent results for the Turkish pharmaceutical sector, which consists of hundreds of small companies having markets shares of 7% at the highest.