Second-half goals from Dudu and Hernan Barcos led Gremio to a 2-0 win at Atletico Nacional's Estadio Atanasio Girardot.
The win sealed Gremio's place in the last 16, with the Brazilian outfit sitting top of Group 6 with 11 points.
Newell's Old Boys (eight points), Atletico Nacional (seven) and Nacional (one) are behind the leaders.
Gremio needed until the 53rd minute to open the scoring as Ramiro's run and cutback from the right found Dudu, who struck into the roof of the net.
Argentine Barcos doubled their advantage on 69 minutes as he burst onto a loose ball, accelerated away from defenders before delicately chipping goalkeeper Franco Armani.
In Rio de Janeiro, Union Espanola secured their last-16 place after a hard-fought 1-0 win over Botafogo.
Gustavo Canales' well-placed 72nd-minute penalty was all the Chileans needed to claim their victory.
Undefeated through five Group 2 matches, Union Espanola (nine points) are ahead of Botafogo (seven), Independiente del Valle (five, -1 goal difference) and San Lorenzo (five, -2).
Flamengo remain alive in Group 7 after a thrilling 2-1 win over Emelec at the Estadio George Capwell.
A handball in the area gave Alecsandro an opportunity to open the scoring for Flamengo, and he finished into the bottom corner.
Emelec needed a spot-kick of their own to level the encounter on 66 minutes.
Former Everton striker Denis Stracqualursi took a different approach to Alecsandro, smashing his penalty down the middle to level at 1-1.
But the visitors struck a dramatic late winner in the 93rd minute.
Guilherme Negueba's long pass from the left found Paulinho on the right side of the area, and the attacker finished brilliantly into the bottom corner to seal three points for his side.
Flamengo (seven points, +1 goal difference) are behind Bolivar (eight) and Leon (seven, +2) in Group 7, while Emelec (six) are bottom.
