Relying on Mexican archival evidence, this article argues that Mexico opposed the U.S. effort to place a quota on Mexican immigration during the late 1920s because pro-quota arguments rested on a presumption of Mexicans’ racially inferiority. The three perspectives of the Mexican government officials Francisco Suástegui, Enrique Santibáñez, and Manuel Gamio demonstrate why Mexicans chaffed at the U.S. quota debate. Each of these perspectives also offers an analytical framework through which historians can understand how Mexican officials hoped the United States and Mexico could resolve the immigration controversy through bilateral negotiation. Finally, these officials’ fears about the quota demonstrate that U.S. immigration policy held significant consequences for diplomatic relations between the United States and Mexico.