This study investigates the impact of regulatory quality on economic growth for the D- 8 countries by applying a panel smooth transition regression (PSTR) model from 1996 to 2019. Few studies considered the relationship between regulatory quality and economic growth. In most of them, the linear relationship between the variables has been examined, and non- linear relationships have not been considered. Therefore in this paper the nonlinear association between regulatory quality and economic growth is being examined. For this purpose, the paper uses the regulatory quality index, GDP growth and other variables including financial development, agricultural raw materials exports, inflation rate and gross capital formation. Our empirical results indicate that there is a non-linear relationship between variables under consideration. The results demonstrate that there is one continuous function with two regime and a threshold at regulatory quality of -0.746. In the first regime, financial development, agricultural raw materials and gross capital formation have a significantly positive impact and inflation rate have a significantly negative impact on GDP. At the second regime, agricultural raw materials exports and financial development have a negative impact and inflation rate and gross capital formation have a positive impact on GDP. The results optained from this paper are consistent with several studies including Koeniger and Silberberger(2015). Since the regulatory quality index in higher levels has a positive impact on economic growth, to achieve a stable economic growth the economic planners and policy makers should pay much attention to creating efficient institutions with transparent regulations.