Georgia Garnett starred in the drought-breaking performance, kicking three goals in the Giants' 8.2 (50) to 3.11 (29) triumph at Manuka Oval on Saturday.
Cam Bernasconi's side busted the game open after a dour first half, piling on seven goals to three after the main break to run away with the result.
The Giants' previous victory - also against the Bulldogs - was in round one last season.
They had gone 378 days without a win, registering 13 losses and a draw in that time.
The result left both sides with 1-4 records after five rounds.
"I'm really proud," Giants captain Rebecca Beeson told Fox Footy.
"The first four rounds haven't gone the way that we wanted but we believe that we're a much better team than we were last year.
"I'm proud of the way we stuck fat and stayed really connected as a group and put in a really good performance today."
Garnett, who had kicked 2.5 across the opening month of the season, was outstanding with 3.1 from 18 disposals.
All three majors came in the crucial third quarter, when the Giants turned a one-point half-time advantage into a match-winning lead with six goals to three.
"The last couple of weeks I've probably shanked a few and missed my opportunities, so I've been getting to work and making sure I stick those when it counts," Garnett told Fox Footy.
"Going into the game we were super pumped. We felt like a win was coming for us because we believe so much in what we're doing."
An Alice Edmonds behind was the only score of the opening term and the wasteful Bulldogs had 0.4 on the board before Taylah Levey (two goals) put GWS in front with the first goal of the game.
It came at the seven-minute mark of the second quarter and helped the Giants to a narrow 1.1 to 0.6 advantage at the main break.
Ellie Blackburn finally kicked the Dogs' first major with a free-kick from the goal square in the opening minute of the third quarter.
It was the first of four lead changes in the third quarter as the game opened up.
Garnett delivered her three goals as the Giants posted 6.1 to 3.3 for the term, turning for home 17 points in front.
And while they had given up leads in the past, GWS never looked likely to fall flat in the final quarter as they kept the Bulldogs at bay.
Emily Pease (29 disposals), Zarlie Goldsworthy (23) and Beeson (21, one goal) were all influential for the Giants, while Isabelle Pritchard and Jessica Fitzgerald (16 touches each) fought hard for the Bulldogs.
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