This article investigates whether regional trade agreements (RTAs) with environmental provisions affect relative and absolute pollution levels. In order to do this, the determinants of convergence of carbon dioxide emissions are estimated for a cross-section of 182 countries in the period from 1980 to 2008. The main results indicate that the CO2 emissions of pairs of countries belonging to an RTA with environmental provisions tend to converge and are lower in absolute terms, which is not the case with RTAs with no environmental provisions. The article states that emissions converge faster for NAFTA than for EU-27 and Euro-Med countries. The study highlights consistent evidence that only RTAs with environmental harmonization policies affect relative and absolute pollution levels.