This study explores the role of U.S. ethnic scientific and entrepreneurial communities for international technology transfer to their home countries. U.S. ethnic researchers are quantified through an ethnic-name database and individual patent records. International patent citations confirm knowledge diffuses through ethnic networks, and manufacturing output in foreign countries increases with an elasticity of 0.1–0.3 to stronger scientific integration with the U.S. frontier. Specifications exploiting exogenous changes in U.S. immigration quotas address reverse-causality concerns. Exercises further differentiate responses by development stages in home countries. Ethnic technology transfers are particularly strong in high-tech industries and among Chinese economies.