Asset pricing models are the subject that has attracted much attention in finance for years. Recently Hou, Xue and Zhang (2015) developed a new asset pricing model and denominated "q-factor model". In the model, the excess returns of risk-free rate are explained by market beta, firm size, investment and profitability factors. In this study, the validity of q-factor model in Borsa Istanbul is investigated by using time series regression method. As per GRS-F test results, it is obtained that q-factor model is valid in Borsa Istanbul. The findings revealed that all four factors are priced between July 2009 and June 2016 in Borsa Istanbul and q-factor model can be used in predicting expected returns.