The environmental Kuznets curve hypothesis is a theory by which the relationship between per capita GDP and per capita pollutant emissions has an inverted U shape. While impressive growth of ASEAN countries in the last few decades has significantly helped improve the people's standard of living and reduce the poverty rates, it has also exerted tremendous pressure on the environment of these countries. The question is whether economic growth and higher income levels can eventually lead to a reduction in environmental pollution, as proposed by Environmental Kuznets curve (EKC) hypothesis. The paper is to investigate the validity of EKC hypothesis for the case of carbon dioxide emissions in ASEAN countries (excluding Brunei), employing a panel data approach for ASEAN countries, using fixed effect and random effect modeling. It is found that EKC does exist for the case of these countries' carbon dioxide emissions, but with a relatively high turning point income (approximately 4000). This suggests that more active policy measures should be taken in the development plans of ASEAN countries so that a decline in carbon dioxide emissions would occur sooner.