We study the labor market impacts of the Permiso Especial de Permanencia program, the largest migratory amnesty program offered to undocumented migrants in a developing country in modern history. The program granted work permits to nearly half a million undocumented Venezuelan migrants in Colombia in August 2018. To evaluate the effects of the program, we compare labor outcomes in departments that have larger and lower treatment intensity, before and after the program roll-out. We test the robustness of the difference-in-difference results to using three alternative instrumental variables, finding consistent estimates regardless of the instrument used. We are only able to distinguish negligible effects of the program on the formal employment of workers. These effects are negative for Colombian workers and positive for Venezuelan workers. For the case of Colombian workers, the effects are concentrated in highly educated and in female workers.