The study attempts to examine the economic, demographic, and development determinants of economic complexity by using annual data spanning from 1995 to 2019. The advanced panel quantile method is employed to estimate the long-run impacts of driving forces on economic complexity along with its distribution. The empirical results reveal several important points. First, income, population density, human capital, and government consumption appear to improve economic complexity while natural resources rent imposes a negative effect. Second, the impacts of such factors are heterogeneous across quantiles of economic complexity. Third, there exist huge differences in the roles of such factors between high-income and middle- and low-income countries. Based on the findings, applicable policies are provided.