Despite having two players sent off in the final 20 minutes on Thursday, Nacional cruised to a big win after both Fernando Uribe and Jefferson Duque notched braces in the opening hour.
The victory took Juan Carlos Osorio's team to 13 points in Group A of the Clausura semi-finals and with Junior (seven points) losing 2-1 away to Santa Fe, Nacional have secured a spot in the final.
Nacional also won the Apertura title with a 2-0 aggregate victory over Santa Fe earlier in the season and the Medellin-based club will take on Deportivo Cali in the Clausura final.
Cali continued their perfect record in the Clausura semi-finals with a 4-2 triumph over Millonarios on Wednesday.
Vladimir Marin got Cali underway in the 28th minute when he smashed home a free-kick from 30 yards.
Millonarios equalised in similarly spectacular fashion with two minutes left in the first half with Harrison Otalvaro curling the ball home from the edge of the area but Cali led at the break following a rocket from Carlos Lizarazo in first-half stoppage time.
Just after half-time, the hosts led 3-1 with Sergio Romero sliding home to stab the ball into the net from close range.
Although Erick Moreno pulled Millonarios within a goal again in the 57th minute, Cali wrapped up their victory when Romero bagged his second, cleverly converting with a back-heel after visiting goalkeeper Luis Delgado failed to hold onto a long-range strike.
The win took Cali to 15 points from five matches, while Millonarios remain bottom of Group B on three points.
Once Caldas moved up to second on six after a 3-1 win over Deportivo Pasto, who dropped to third on goal difference.
