This article analyses the enfranchisement process of the prison population in Chile. Although institutions were reluctant to grant the vote to this group for several years, in 2022, new policies allowed prisoners to suffrage for the first time. The Voto Preso movement, a set of organisations struggling for prisoners’ political participation, played a fundamental role in this transformation. However, incarcerated people's participation in constructing the movement's demands and strategies was scarce. Drawing on eleven interviews with key movement actors, the article sheds light on the main discourses by which it promoted the materialisation of Chilean prisoners’ voting rights. The article also critically scrutinises the consequences of prisoners’ limited inclusion in the Voto Preso movement. Finally, the article discusses how its analytical approach may open new avenues for studying prisoner dis/enfranchisement as a situated boundary issue.