Global warming is a serious problem facing the world today. To minimize it, scholars are trying to find the reasons behind increasing CO2 emissions. This study examines the effects of overall export product diversification, extensive margin, and intensive margin on CO2 emissions as indicators of environmental degradation in 84 developing countries for the period of 1971-2014 in the context of the environmental Kuznets curve (EKC) hypothesis using three estimators, namely, autoregressive distributed lag (ARDL) bounds test, dynamic ordinary least squares (DOLS), and fully modified ordinary least squares (FMOLS). The empirical findings reveal that EKC hypothesis is valid. The overall empirical findings from various approaches show that overall diversification, extensive margin, and intensive margin have a positive and significant effect on CO2 emissions.