Debates about lowering the voting age often center on whether 16- and 17-year-old adolescents possess sufficient cognitive capacity and political knowledge to participate in politics. Little empirical research has examined age differences in adolescents' and adults' complexity of reasoning about political issues. We surveyed adults (n = 778; M[subscript age] = 38.5, SD = 12.5; 50% female; 72% non-Hispanic White) and 16- and 17-year-old adolescents (n = 397; 65% female; 69% non-Hispanic White) concerning judgments and justifications about whether the United States should change the minimum voting age. Justifications for changing the voting age were coded for integrative (i.e., integrating multiple perspectives to form a judgment about changing the voting age), elaborative (i.e., providing multiple reasons to support the same judgment about changing the voting age), and dialectical (i.e., recognizing multiple differing perspectives on changing the voting age) complexity of reasoning. Bayesian regressions indicated that adolescents provided greater integrative and elaborative complexity in their reasoning to change the voting age than adults. Adolescents and adults did not meaningfully differ in their dialectical complexity. Findings are consistent with past research indicating that adolescents possess the cognitive capacity and political knowledge to vote in U.S. elections.