Teachers unions play a major role in education policymaking in Latin America. In this paper, we review the literature and document cases where unions have likely had a positive impact on education. This has been primarily through their effect on the professionalization of the teaching force and their policy advocacy. Through publications, courses, and leadership opportunities, unions likely have positively contributed to instruction and teachers’ sense of purpose. Through policy advocacy, unions have informed governments of crucial local knowledge, have contributed research, and have established mechanisms of collaboration. We make the following policy recommendations: 1) Encourage unions’ professionalizing activities for teachers; 2) Establish institutionalized spaces where teachers can participate in the making of education policy, regardless of the government in power; and 3) Plan education policy democratically, incorporating unions.