The mitigation of global warming by reducing greenhouse gas emissions has been the objective of successive negotiations and agreements between nations. At the same time, there is a consensus on the virtues of export diversification for the development of less advanced countries. This article investigates the effect of export diversification on CO2 emissions in the context of an environmental Kuznets curve hypothesis in 98 developed and developing countries during the period 1995-2013. Using short-run (system Generalized Method of Moments) and long-run (Pooled Mean Group) estimation methods, we find that the environmental Kuznets curve is valid and that export diversification has a positive effect on CO2 emissions. (c) 2019 John Wiley & Sons, Ltd.