International treaties have mostly failed to produce their intended effects except for international trade and financial laws and treaties with enforcement mechanisms. These results are unexpected because they challenge conventional wisdom about treaties, which are widely considered as the apex mechanism for countries to make commitments to each other. Not only do our findings question the usefulness of the more than 250,000 existing treaties that have been negotiated to date but they should directly inform how national governments and international institutions facilitate global cooperation on the myriad challenges we face and how future international treaties can be better designed for greater impact.