This rapid review synthesises the literature from academic, policy, and knowledge institution sources on how reform in customs procedures can facilitate international trade in environmental goods and services. Overall, it finds that there is a general belief in the literature from the World Trade Organization (WTO), International Trade Center and World Bank, that streamlining customs procedures supports international trade in environmental goods. There is survey evidence that firms exporting environmental goods encounter difficulties with customs procedures at the point of entry. Previous trade facilitation projects have not considered trade in environmental goods, so provide no evidence about what has or has not worked well. The evidence base identified during this literature review was extremely small, and came largely from international trade institutions such as the WTO or World Bank, or research organisations working with them. Most of the references to trade in EGS and customs procedures were mentioned in passing as mutually compatible without going into further detail. One of the few documents to combine trade in EGS with trade facilitation is not available for public viewing.