Achieving the continuous and consistent economic growth is one of the most important economic goals of each country. Identifying the effective factors on economic growth is a useful tool for adopting sound economic policies. For this reason, this study empirically examines the impacts of trade openness, foreign direct investment, and financial development on economic growth across 64 countries over the period 1995-2016. All data in this study are taken from World Bank, World Development Indicator online database and transformed into natural logarithms form. We selected the period and countries based on the availability for all the data series. The countries are divided into two groups: low-income and high-income group countries, following the World Bank’s income classification. We employ the panel unit root tests, Pedroni cointegration tests, Pooled Mean Group (PMG), Mean Group (MG) and Dynamic Fixed Effects (DFE) estimation techniques on cross-country panel data. However, to select among PMG, MG, and DEF estimators, Hausman test is utilized. According to this test, the PMG estimator is chosen for both groups of countries since it is more efficient. The contribution of this study is two-fold. First, this is the first study that attempts to evaluate the impacts of trade openness, FDI, financial development on economic growth in high- and low-income countries. Second, this study is different from previous studies on the relationship among the trade openness, FDI, financial development and economic growth in the econometric method. For high-income countries, the results indicate that the trade openness positively and significantly impacts on economic growth both in the long as well as short run. The financial development has a negative and significant impact on economic growth in the long run and no impact in the short run. We find that long-run coefficient of the foreign direct investment is significant and contribute positively to the economic growth. In addition, on the basis of the econometric analyses for the low-income countries, the trade openness has a positive and significant coefficient in long run but negative and insignificant coefficient in the short run. The variable of the financial development has a negative and insignificant impact on economic growth in both long- and short-run. Also, the findings suggest an insignificant and positive impact of the foreign direct investment on economic growth in both short and long run. Thus, the study concludes that trade openness and foreign direct investment have played the more important role in improving the economic growth in the high-income group countries than low-income countries.