Millonarios missed the chance to gain the outright lead atop the Colombia Primera A table as Junior moved level at the summit.
Juan Manuel Lillo's Millonarios were beaten 2-1 by Medellin at the Estadio Atanasio Girardot on Tuesday, meaning they are now level on 27 points alongside Atletico Nacional and Junior after 14 games.
With Nacional slipping up at the weekend, Millonarios had the opportunity to jump two points clear.
But second-half goals from Luis Tipton and German Cano ended Millonarios' five-game winning streak on a disappointing night for the visitors.
Both teams failed to make any sufficient inroads until Tipton found the back of the net eight minutes after the interval.
The Colombian defender made a dashing run towards the penalty area before scoring with the outside of his left foot.
Millonarios were back on level terms in the 77th minute when Wesley bundled the ball over the line after a goalmouth scramble, however, Cano pounced on a goalkeeping howler to secure maximum points with seven minutes remaining.
At the Estadio Metropolitano Roberto Melendez, Junior came from behind to defeat Boyaca Chico 2-1 on Wednesday.
A brace from Martin Arzuaga cancelled out Juan Perez's opener as Junior made it four wins on the bounce.
Elsewhere in Colombia, Santa Fe are two points adrift despite overrunning Deportivo Pasto 3-2 on Tuesday.
Once Caldas are a point further back in the standings after recording a comfortable 3-1 victory at home to Uniautonoma, who remain second from bottom.
Cellar dwellers Fortaleza were triumphant on Thursday, claiming a rare 2-1 win against Envigado courtesy of Jorge Ramos' second-half double.
In other results, Deportivo Cali slumped to a 2-1 defeat at the hands of Alianza Petrolera, Itagui accounted for 10-man La Equidad 3-1, while Deportes Tolima overcame Patriotas Boyaca 2-1.