This paper investigates the validity of the Environmental Kuznets Curve hypothesis by considering the income level of 101 countries from 1990 to 2019. The study utilizes panel regression and panel ARDL estimation in its methodology. The robustness check of the model using cointegration test shows a long run relationship exist between the variables. The results show that the EKC holds true for high and middle-income countries but not for lower-income countries, with an inverse U-shaped curve for the former and a U-shaped curve for the latter. The study finds that upper middle-income countries have the highest threshold of productivity beyond which CO2 emissions reduce, while lower-income countries require the least threshold of productivity beyond which CO2 emissions exacerbate. The study reveals that trade openness is not significant in explaining the change in CO2 emissions, except for upper middle-income countries. The findings provide valuable insights into the income-emissions relationship to guide policy to promote sustainable development.