In perfect conditions at Canberra Stadium, the Brumbies were unlucky to be behind 13-10 at halftime after a tight contest.
The Cheetahs looked nothing like the side that were pummelled 51-19 by the Bulls last weekend, and looked to trouble the home side early with their pace in attack.
The boot of Johan Goosen may have well ended up the difference with the Cheetahs' goalkicker - who had yet to miss in 2012 - nabbing five from six attempts for the day.
But with each team finishing with two tries each, it was the Brumbies that managed to rein in the Cheetahs in the dying seconds to pull off a stunning win.
Both teams scored a try in the first half - the Brumbies' coming in the ninth minute through winger Henry Speight, who was the beneficiary of an impressive 20m run from speedy halfback Nic White.
The Cheetahs responded in the 19th minute when winger Willie Le Roux made a brilliant break through the middle of the field to put the Cheetahs up for the second time in the game.
Tewis de Bruyn crossed for the Cheetahs in the 47th minute and when Goosen kicked another penalty a minute later, the South Africans had built a commanding 23-10 advantage.
However, that was the last time they would register points as the Brumbies slowly whittled away their lead.
Winger Pat McCabe crossed for a 52nd-minute five-pointer, and while Lealiifano missed the conversion, successful penalty kicks in the 65th and 75th minutes brought them to within two points before his last-gasp heroics.
BRUMBIES 24 (Pat McCabe, Henry Speight tries Christian Lealiifano con 4 pens) bt CHEETAHS 23 (Tewis de Bruyn, Willie Le Roux tries Johan Goosen 2 cons 3 pens) at Canberra Stadium.
- AAP