The Mensalao trial was Brazil’s most important political corruption trial ever and an emblematic ex post accountability success. More than 28 individuals were convicted in relation to a legislative vote-buying scheme, many by the very officials they helped appoint. We relay the trajectory of the scandal cum trial, explain its successful prosecution, and assess its implications. The paper argues that the Mensalao has proved pivotal for Brazil’s institutional and legal advances and asks – more than a quarter of a century after a new constitution – whether the country is entering into a stronger, more enduring relationship with the rule of law.