This paper presents the first comprehensive analysis of corporate environmental disclosure (CED) in the Arab MENA region. Using a detailed research instrument containing 55 items, content analysis of the annual reports of 180 non-financial companies listed on nine major stock markets was conducted over a five-year period. The calculation of an unweighted disclosure index indicates that, although the level of disclosure might be considered relatively low by international standards, it varies by country. Perhaps of greater significance for the future of sustainable development in the region, disclosure is shown to have increased significantly over the period 2010-2014. Further analysis shows that, although there are some differences relating to categories of disclosure, this is a region-wide phenomenon not driven by a subset of countries or types of company. This benchmark study provides a systematic picture for policy makers in the region and, for future researchers, both substantive findings and methodological insight.