The Force overcame four yellow cards to open their season with two victories for the first time in Super history, coming after their home win over Moana Pasifika in round one.
They reclaimed the lead in the 75th minute when reserve hooker Brandon Paenga-Amosa burrowed over after 18 phases, and they managed to hold out the desperate home side for a famous victory.
It looked like it would be match the visitors would remember for all the wrong reasons after letting slip a 21-0 lead midway through the first half.
Hooker Nic Dolly, wingers Harry Potter and Dylan Pietsch and Carlo Tizzano all crossed, with the Force playing with intent and purpose.
The home side were bolstered by the inclusion of four Wallabies in Allan Alaalatoa, James Slipper, Tom Wright and Len Ikitau, who sat out their round-one win in Suva, but the Brumbies looked unsettled early on, making uncharacteristic mistakes.
There was still a healthy 28-14 buffer at halftime, but the Force’s poor discipline started to undo their good work.
The Brumbies scored three tries either side of halftime, while Force No.8 Reed Prinsep was off the field for a clumsy tackle that also left flanker Tom Hooper ruled out of the match with concussion.
Winger Corey Toole crossed in the 53rd minute to give the home side the lead for the first time, but five minutes later flying Force recruit Pietsch was in for his second.
Brumbies No.8 Charlie Cale bagged his second for his team to again go ahead, then the Force lost both skipper Jeremy Williams and Nicholas Champion de Crespigny to yellow cards.
Playing with only 13 men for five minutes and trailing 42-38, it appeared the visitors would be denied.
But they showed their grit to hammer the home side’s line, before Paenga-Amosa came up with the match-winner.