Striker Michelle Heyman continued her stellar form for Canberra with a brace, taking her season tally to 12 goals, with Taryn Hemmings scoring two of her own to seal the match.
But apart from a purple patch in the first half and a disappointing finish, Adelaide did well to contain their highly-fancied rivals, and had some very near misses themselves.
From the outset Adelaide showed spirit to keep Canberra at bay for the first 25 minutes, with the ball locked in the midfield and neither team able to threaten the goals.
Eventually Canberra broke the stalemate in the 28th minute, when Heyman clashed with Adelaide goalkeeper Sian McLaren to win a bouncing Grace Gill long ball and find the back of the net.
Six minutes later Canberra and Heyman had their second, when she beat Anna Green to a Hayley Raso through ball, tapped it past McLaren and finished from a tight angle.
Canberra started the second half in a flurry, with Hemmings coming on and in the thick of it, having a couple of shots on goal and creating a half chance with a blocked clearance.
Adelaide nearly pegged one back when Racheal Quigley headed on target, but substitute goalkeeper Aroon Clansey was up to the challenge.
To their credit, Adelaide showed a lot of fight in the second half and had the better chances.
Marijana Rajcic nearly scored their first, but again Clansey was up to the task with a fine save parrying it out.
Canberra seemed unlucky to have cries for a penalty turned down in the 76th minute, when Ashleigh Sykes was brought down by a sliding Abby Erceg.
They ended up breaking through minutes later, with Hemmings weaving her way through four defenders and putting it along the carpet into the bottom left corner.
Two minutes later she had her second, this time trying her luck from long range with her left and curling it into the top right corner.
Adelaide came close to a consolation goal with a few minutes left, Rajcic beating Clansey but unable to regather possession as an open goal went begging.
Sykes made it five for Canberra with the last kick of the game, finishing well from a difficult angle on the right.
Canberra United 5 (Heyman 28, 34, Hemmings 83, 85, Sykes 90)
Adelaide United 0