Luke Beveridge's side flexed their muscles with five unanswered goals in the third quarter to set up a 17.11 (113) to 12.9 (81) victory at Canberra's Manuka Oval on Saturday night.
The Bulldogs (4-3) move into seventh place on the ladder ahead of Sunday's matches, having defeated the Giants in eight of their nine meetings since 2020.
"Over the moon," Beveridge declared.
"We were a bit rattled early. We went in knowing that they were going to have a reasonably strong intercept presence.
"Their key backs have got terrific craft, they position well, so we knew being a tall short down there, we were going to need to use the ball well in a certain way.
"After quarter time, the boys had a real resolve and that's one of the reasons we definitely got on top, because we had to take their intercept game off them."
Sam Darcy's absence through injury was covered by recalled James Harmes (four goals), while captain Marcus Bontempelli had his usual influence before being managed out in the final term.
Joel Freijah also starred with 27 disposals, nine clearances and 19 contested possessions after recovering from a hit to the head in the third quarter.
The 19-year-old, with his head over a ground ball, was collected by a side-on Tom Green. A free kick was paid against Green.
The Giants (4-3) drop from fourth to sixth after suffering back-to-back defeats.
"It's not an effort question. We were trying, we just couldn't manage it," GWS coach Adam Kingsley said.
"To have that third quarter on the back of a strong first half, but then compound that into the Adelaide game the week before, we've got some things to work out."
Jake Riccardi led the Giants with three goals, as Jesse Hogan kicked two on return from a calf injury.
GWS defender Lachie Ash finished with a game-high 31 disposals, while Lachie Whitfield shook off an ankle complaint to finish with 30.
Whitfield had limped off the ground in agony late in the first term after taking an innocuous kick outside of the contest, and played on with heavy strapping.
Riccardi kicked two first-quarter goals as the Giants had the better of the play early, boasting a six-point lead at the first break.
The second term was a see-sawing affair, with the Bulldogs soaring to lead by 13 points, before Hogan and Toby Bedford levelled the scores at 7.5 (47).
Giants skipper Toby Greene (two goals) could only give his side a one-point lead when his soccer kick hit the post.
And the lead was short-lived, with Tim English slotting a major after the siren thanks to a rucking infringement by Giants counterpart Kieren Briggs.
The Bulldogs emphatically shut out their opponents from the contest to kick 5.3 to 0.1 in the third quarter, and reached a game-high 52-point lead on their way to victory.
Bulldogs debutant Jedd Busslinger, replacing an omitted Liam Jones, provided an early highlight in the opening term when he denied Darcy Jones' left-foot snap at goal with a mark on the line.
He subsequently gave up possession to Finn Callaghan, but the highly rated Giants midfielder matched his gaffe in the next play.
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