Coinciding with the shift to the left in Latin American politics, regional integration in Latin America accelerated during the last two decades. Yet, whereas support for European integration has been tracked systematically for decades, trend analyses of public opinion on Latin American integration are still missing. Combining data from eight Latinobarometer surveys on 106,590 respondents from seventeen South and Central American countries, this article provides the first longitudinal analysis of Latin Americans’ support for their continent’s economic and political integration. Using multilevel mixed-effects logistic regression, we reveal intra- and intersocietal trends and cleavages. Our results show that support rates are generally declining from high initial levels. Furthermore, while gender and educational gaps in public opinion remained stable over time, considerable shifts occurred with regard to political orientation: starting from the lowest initial values, the left surpassed the right—and, at least in the case of support for political integration, also the center—to become the political wing favoring integration most highly. This finding shows, contrary to prevailing ideas, that the political center is not necessarily the primary supporter of integration. When regionalism is increasingly driven by left-wing governments, public support for regional integration may also swing to the left.