This study examined the impacts of upgrades and downgrades by the three big major rating agencies (Standard and Poor’s, Moody’s and Fitch) on Turkey’s stock market. §The Istanbul Stock Exchange National 100 Index (XU100) was used as stock market indicators. The data set covers the period 1995 and 2011 and quarterly data was used. Control variables were growth rate of GDP per capita and real interest rates. The findings show that rating changes significantly affect the XU100 and vice-versa. GDP growth per capita affects XU100 positively and real interest rates negatively.