To what extent does immigration affect the economic institutions in destination countries? While there is much evidence that economic institutions in developed nations are either unaffected or improved after immigration, there is little evidence of how immigration affects the economic institutions of developing countries that typically have weaker institutions. Using the Synthetic Control Method, this study estimates a significant and long-lasting positive effect on Jordanian economic institutions from the surge of refugees from the First Gulf War. The surge of refugees to Jordan in 1990–1991 was massive and equal to 10 percent of Jordan's population in 1990. Importantly, these refugees were able to have a large and direct impact on Jordanian economic institutions because they could work, live, and vote immediately upon entry due to a quirk in Jordanian law. The refugee surge was the main mechanism by which Jordan's economic institutions improved in the decades that followed.