The immigration control experience when traveling between Argentina and Uruguay
While most people that visit Colonia, Uruguay do it as a day-trip from Buenos Aires and it’s just a quick ferry ride across the Rio de La Plata, the immigration procedure when making the trip is similar to that of a long international trip since they are different countries.
After completing the check-in process and getting your ticket and boarding pass at the ferry port in Puerto Madero, Buenos Aires you will proceed up an escalator to the customs and immigrations area. You will have to pass your bags through an x-ray machine first and a metal detector. Next you will get to immigrations, where there are several booths with immigrations officials. After they call you, you will first legally leave Argentina with an exit stamp. Next the Uruguayan immigration official sitting immediately next to the Argentine agent will do the entrance procedure for Uruguay and stamp the entrance stamp in your passport.
Since you do both countries’ immigration processes in Buenos Aires you will not do immigrations at arrival in Colonia, but will have to put your bags through an x-ray machine again at arrival for Uruguayan customs.
For the return to Buenos Aires the process is the same but in reverse, with you having to do both Uruguayan and Argentine immigrations in Colonia.