The Brumbies looked to be heading for victory following a Folau Fainga'a hat-trick, but they were unable to hold off the Highlanders.
Folau Fainga'a scored a hat-trick for the Brumbies but they fell to a last-gasp defeat against the Highlanders, with the Chiefs and Hurricanes also victorious in Super Rugby on Saturday.
Josh Ioane converted Teariki Ben-Nicholas' 83rd-minute try beside the posts as the Highlanders snatched a 23-22 triumph over the Brumbies at GIO Stadium.
Ioane had eight points from the tee to send Aaron Mauger's team into half-time with a 13-12 lead despite a double from Fainga'a.
But Fainga'a completed his treble with 12 minutes remaining and Ryan Lonergan added the extras before converting a penalty to send the Brumbies six points clear.
However, the hosts committed three penalties as they defended their try line with the clock in the red and, after Murray Douglas was sent to the sin bin, Ben-Nicholas and Ioane forced them to settle for a losing bonus point.
It was an important win for the Highlanders after they began their season last weekend with a heavy loss to the Sharks, who were unable to build on that triumph and went down 38-22 against the Hurricanes in Wellington.
The Sharks were without Curwin Bosch for personal reasons and saw Boeta Chamberlain and Makazole Mapimpi exit the game early due to failed head injury assessments.
Two tries apiece sent the teams into half-time level but Ben Lam crossed twice within 11 minutes of the restart to put the Hurricanes in control.
Dane Coles touched down from the back of a driving maul to extend their advantage but Mzamo Majola went over to deny the hosts a try-scoring bonus point.
The Chiefs became the only team to have won all three of their games this season by overcoming the Sunwolves 43-17 in Tokyo.
Warren Gatland's side responded to Garth April's opener by running in seven tries from as many players, one of which saw Lachlan Boshier run the length of the field while team-mate Tyler Ardron was in the bin for repeated infringements.