Flanker Liam Messam and replacement back Robbie Robinson scored tries four minutes apart deep in the second half and stand-off Aaron Cruden added 17 points with his boot to rescue the home side from a potential upset.
The Brumbies, trying to become the first team to win the title having played their semi-final on another continent, had led 22-12 in the 65th minute courtesy of a converted try and five penalties from centre Christian Lealiifano.
The Chiefs are the fourth team to win back-to-back titles and join the Auckland Blues, Canterbury Crusaders, Bulls and Brumbies as multiple winners of the southern hemisphere’s flagship competition.
“I think it was a real tough final,” said Chiefs co-captain Craig Clarke, one of string of senior players moving on at the end of the season. “We have to pay credit to an awesome Brumbies team for a hell of a performance, especially after all the travelling they’ve done.
“It’s been an awesome couple of seasons and a great group to be part of. Big ups for what we have done.”
For much of the evening, though, it looked like the Canberra-based Brumbies might just become the first foreign team to win the title on New Zealand soil.
Kicking for territory and targeting the breakdown, the visitors raced out to a 9-0 lead in the first 20 minutes on the back of three Lealiifano penalties. The hosts, though, got over their slow start and started to ramp up their attack.
“We led from the start and for them to come from behind speaks loads for this Chiefs team,” Brumbies skipper Ben Mowen said. “They are an outstanding champion side.”