The Kings outscored the Brumbies four tries to two to claim a dramatic 28-all draw at Canberra Stadium on Friday.
Kings number eight Cornell du Preez score his second try of the game after the final hooter before Demetri Catrakilis slotted the conversion to seal the biggest upset of the Super Rugby season so far.
The result sees the Brumbies lose their lead in the overall standings (on points difference to the Chiefs) while the Kings climb up to twelfth.
The Brumbies led 19-14 at half time but, contrary to all expectations, the Kings took the lead early in the second period after a wonderfully executed try, the visitors' third of the evening.
Five penalties from fly-half Christian Lealiifano were enough to give the Brumbies what had looked like a match-winning lead until the last moments.
Impressive with their physicality and well-organised defence, the Kings never allowed the Brumbies to get their attack going and pounced on opportunities when they were presented.
The opening quarter went according to script as the Brumbies cruised to a 13-0 lead thanks to tries from Henry Speight and Joe Tomane.
But the team from Port Elizabeth weren't prepared to roll over quietly and bounced back via tries from prop Schalk Ferreira and flank Wimpie van der Walt to narrow the gap to just two points.
Penalties from Lealiifano and Nic White ensured the hosts reached the break narrowly ahead, but du Preez rounded off a great try from a move started in their own 22 to throw a cat amongst the pigeons early in the second-half.
Lealiifano was able to put the Brumbies back in front from the kicking tee and the Kings' spoiling tactics at the breakdown were eventually punished by a yellow card for Ferreira.
Lealiifano was on target twice to stretch the lead to seven points in the final ten minutes and it looked to be enough as referee Jaco Peyper signalled full time with the kings camped on the Brumbies line. But a call from the assistant referee gave the Kings one last penalty and du Preez crashed over from short range.
Tries: Speight, Tomane
Pens: Lealiifano 5, White
Tries: Ferreira, van der Walt, du Preez 2
Cons: Whitehead 3, Catrakilis
Yellow card: Ferreira
Brumbies: 15 Robbie Coleman, 14 Henry Speight, 13 Tevita Kuridrani, 12 Pat McCabe, 11 Joe Tomane, 10 Christian Lealiifano, 9 Nic White, 8 Fotu Auelua, 7 George Smith, 6 Ben Mowen (c), 5 Etienne Oosthuizen, 4 Peter Kimlin, 3 Dan Palmer, 2 Siliva Siliva, 1 Ben Alexander.
Replacements: 16 Stephen Moore, 17 Scott Sio, 18 Sam Carter, 19 Colby Faingaa, 20 Ian Prior, 21 Andrew Smith, 22 Zack Holmes
Kings: 15 Siviwe Soyizwapi, 14 Sergeal Petersen, 13 Waylon Murray, 12 Andries Strauss (c), 11 Ronnie Cooke, 10 George Whitehead, 9 Nicolas Vergallo, 8 Cornell du Preez, 7 Wimpie van der Walt, 6 Devin Oosthuizen, 5 Rynier Bernardo, 4 Steven Sykes, 3 Grant Kemp, 2 Hannes Franklin, 1 Schalk Ferreira.
Replacements: 16 Bandise Maku, 17 Kevin Buys, 18 David Bulbring, 19 Jacques Engelbrecht, 20 Shaun Venter, 21 Marcello Sampson, 22 Demetri Catrakilis.
Venue: Canberra Stadium, Canberra
Referee: Jaco Peyper (South Africa)
Assistant referees: Angus Gardner (Australia), Andrew Lees (Australia)
TMO: George Ayoub (Australia)