The Trans-Pacific Partnership (TPP) is one of the proposed mega-free trade agreements. While several previous studies have measured the economic impact of the trade liberalization resulting from the TPP, the TPP may have not only a very large economic impact, but also a significant environmental impact, such as changes in greenhouse gas (GHG) emissions. The purpose of this paper is to contribute to the debate over TPP and GHG emissions by asking the following question: Will the TPP increase or decrease GHG emissions? We estimate the potential impact on GHG emissions changes caused by the TPP using the Global Trade Analysis Project (GTAP) model, and the GTAP CO2 and non-CO2 emissions databases. Our results suggest that the TPP is likely to increase the total amount of GHG emissions in the 12 TPP member countries, as well as global emissions. The main reason for increasing TPP member and global GHG emissions is non-CO2 emissions growth in Australia and the US.