The Power led by 40 points late in the third quarter, but the Suns, with Peter Badcoe VC medallist Michael Rischitelli, captain Gary Ablett and young stars David Swallow and Charlie Dixon outstanding, piled on six goals to the Power's one in the final term to snatch the lead with two minutes to play.
Showdown hero Justin Westhoff had a chance to break Gold Coast hearts with a shot at goal after the final siren, but his kick missed to the right and the visitors celebrated a memorable victory, 15.14 (104) to 15.11 (101).
Ablett and Swallow combined for 19 disposals in the last term, while Dixon and impressive forward Brandon Matera each kicked two goals.
Matera (four goals) led the goalkicking for the Suns, while Daniel Motlop booted four for the Power.
Rischitelli racked up 31 disposals and two goals in a best-on-ground performance. Hamish Hartlett was Port Adelaide's best with 24 disposals, nine tackles and two goals.
The Power were dealt a blow before the opening bounce, losing ruckman Dean Brogan to a leg injury and it didn't take long for the Suns to capitalise on his absence.
Josh Fraser and impressive big man Zac Smith dominated the hit-outs.
The Suns also won the clearances, but conceded two goals from turnovers in the first quarter and trailed by 19 points at the first change.
Port Adelaide extended its lead to 23 points at half time and kicked another five goals in the third quarter to lead by 40 points at the 28-minute mark, but unlike last week the Suns persisted in the final term and staged a remarkable upset.
Port Adelaide 5.3 9.5 14.7 15.11 (101)
Gold Coast 2.2 5.6 9.9 15.14 (104)
GOALS
Port Adelaide: Motlop 4, Hartlett 2, Surjan 2, Boak, Ebert, C. Cornes, Westhoff, D. Stewart, Davenport, Trengove
Gold Coast: Matera 4, Rischitelli 2, Dixon 2, Russell 2, Brennan, Smith, McKenzie, Ablett, Bennell
BEST
Port Adelaide: Hartlett, Motlop, Westhoff, Surjan
Gold Coast: Rischitelli, Matera, Ablett, Swallow, Dixon
INJURIES
Port Adelaide: Dean Brogan (achilles) replaced in selected side by Daniel Stewart
Gold Coast: Matt Shaw (general soreness) replaced in selected side by Maverick Weller
SUBSTITUTES
Port Adelaide: David Rodan replaced by Jason Davenport in the third quarter
Gold Coast: Daniel Gorringe replaced by Luke Russell in the third quarter
Reports: Nil
Umpires: Kennedy, Leppard, Hay
Official crowd: 21,287 at AAMI Stadium
