The ACT side eventually ran out 62-36 winner in Canberra on Saturday.
The match saw the lead change five times until the Brumbies, on the back of a strong lineout, took control of the game in the final quarter.
The Brumbies put on four late tries and Moana Pasifika ran out of steam in the final 20 minutes.
New flanker Miracle Fa'ailagi set the tone in in the second minute when he took an intercept and galloped 70 metres to score.
As if that wasn't enough of a scare then Alamada Motunga scored from a lineout to make it 10-3 thanks to a Noah Lolesio penalty in the fifth minute.
Christian Leali'fano added the extras for Moana Pasifika to lead 14-3 in the 11th minute and it looked an upset was on.
Winger Timoci Tavatvanawi was sinbinned for sticking a boot out at a breakdown and the Brumbies made the most of Moana Pasifika being a man down when they drove from a lineout for flanker Luke Reimer to score the first of his two tries. Lolesio converted and the Brumbies had the lead again at 22-17.
Fine Inisi scored next for Moana Pasifika to have level 22-22 two minutes from the break.
Again the Brumbies drove from a lineout for Remer to poke through complete his brace and with the try converted the Brumbies went to the break ahead 29-22.
Three minutes after the restart Motunga scored and with the try converted it was now 29-29.
With off-loads going thick and fast, winger Andy Muirhead put the Brumbies in front in the 46th minute for an unconverted try.
Moana Pasifika put in a lineout drive of their own for hooker Tasman Mako to go in for a converted try in the 53rd minute.
Around the three quarter mark Jack Debrecenzi waltzed in with replacement halfback Ryan Lonergan making no mistake with the spot kick.
Moana Pasifika started to tire after that and Muirhead gain his second try which was converted by Lonergan to take the score to 48-36.
Ben O'Donnell ran a superb support line finish over the line and the conversion made it 55-36.
Then the coup de grace as Muirhead found Toole with a long pass and the winger scampered over and with the conversion from Lonergan the score was 62-36.