The two clubs started Thursday in the bottom four in Colombia's top tier but victories over Envigado and Deportes Tolima respectively, saw Cali and Medellin move up the table.
In Santiago de Cali, Carlos Rivas and Rafael Borre scored as the home side defeated Tolima 2-0, while Medellin also won at home, coming from behind to triumph 3-2 thanks to a late brace from German Cano.
Cali started their match in second-last position with just three wins to their name in the Apertura campaign but hit the front in the 19th minute when Rivas volleyed home from near the penalty spot.
A corner in the 32nd minute saw Cali double their lead with Borre getting free of his marker to glance a header into the bottom corner.
The victory took Cali to 16 points in 15th, four points and three spots ahead of bottom club Uniautonoma, and just one position behind Tolima (17 points).
Medellin moved above Tolima into 13th with 18 points after their comeback win.
Jonathan Alvarez's scintillating strike gave Envigado the lead in just the second minute in Bogota as he thrashed the ball in off the underside of the crossbar from 25 yards.
The visitors moved 2-0 ahead in the shadows of half-time when Nelson Lemus' header from a cross by captain Neider Morantes was deflected into the net.
Envigado handed Medellin a way back into the match in the 68th minute, with Andres Orozco conceding an own goal from a corner, and the home side drew level 12 minutes later when Cano beat visiting goalkeeper Victor Soto with a close-range header.
Cano completed Medellin's comeback in the second minute of stoppage time, tapping in from Yorley Mena's fine cutback.
At the top of the Primera A table, Millonarios missed the opportunity to move three points clear of Atletico Nacional as they lost 2-1 at Alianza Petrolera.
Nacional did not play during the week due to their Copa Libertadores commitments and Millonarios could have pulled away from the reigning champions but two red cards saw them stumble at Alianza's home ground.
The hosts led at half-time on Tuesday through Ayron del Valle but after Millonarios lost Roman Torres to a red card in the 67th minute, the visitors equalised seven minutes later when Harrison Otalvaro scored.
Alianza went ahead again with 10 minutes remaining, however, with Henry Rojas finding the back of the net, while Millonarios finished the game with nine players after Lewis Ochoa was given his marching orders in stoppage time.
The result left Millonarios on 30 points from 16 games with a plus 11 goal difference, while Nacional (30, plus 13) have a game in hand and remain in first place.
Junior (30, plus five) joined them at the top of the table with a 1-0 win over Deportivo Pasto, while in other results, La Equidad won 2-1 at Patriotas Boyaca, Fortaleza and Boyaca Chico played out a goalless draw and Atletico Huila defeated Once Caldas 2-0.
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