Last seasons third-placed side in the Brazilian championship have improved their squad with the acquisition of an Argentina international from Palmeiras and two players on loan
Barcos, who has four caps for Argentina, wanted to stay in Brazil’s top flight to remain in contention for La Albiceleste.
The deal will cost Gremio €2.5m, part of which goes to LDU Quito in Ecuador, who Palmeiras still owe money to over the signing of Barcos, and the rest to Sao Paulo.
The Tricolour will also loan five players to Palmeiras as part of the transfer including former Wigan Athletic player Marcelo Moreno, defenders Leandro and Vilson, midfielders Rodinelly and Leo Gago, as well as striker Leandro.
Gremio have also taken Welliton from Spartak Moscow and Chilean Eduardo Vargas from Napoli on temporary deals, as they gear up for a Libertadores campaign which sees them face compatriots Fluminense, Caracas of Venezuela and Huachipato from Chile in the group stage.