After St Kilda and Brisbane did the right thing by the Crows, Adeladie only had to win and it would finish sixth.
But Fremantle's shock 17.18.120 to 11.17.83 victory, only its second of the season, relegated the Crows to eighth place and booked them a first-up finals meeting with Carlton.
The Crows had a scare when star midfielder Simon Goodwin left the field in the second quarter with an injured ankle.
The All-Australian sat out the remainder of the quarter with ice on his ankle but returned after half time to see out the game.
The Crows were in the hunt after a hard fought first half when the scores were level at 8.9.57 apiece.
But the Dockers, led by best-on ground Peter Bell who collected 44 possessions and booted three goals, blew the Crows away in the second half.
Bell landed a crucial snap at the 10th minute mark of the final term just as Adelaide had fought back to within 13 points.
That sealed the issue as the Dockers lifted to boot the next three goals.
Best for Adelaide was dual Norm Smith medallist Andrew McLeod.
The match started with a tribute to retired star Tony Modra who was a crowd favourite at both clubs.
Fremantle now claim Modra as one of its own after the high flying full forward finished his career in the west and the Dockers came out determined to give him a fitting send-off.
They led by four points at the first change after utility Ben Cunningham booted two opening quarter goals.
Cunningham continued to pose a threat in the second quarter and added another goal to keep the Dockers level at the main break and set the scene for the second half demolition.
Scoreboard:
FREMANTLE: 4.3, 8.9, 13.15, 17.18 (120)
ADELAIDE: 3.5, 8.9, 9.13, 11.17 (83)
Goals: Fremantle: B Cunningham 3 P Bell 3 D Schell 2 J Longmuir 2 H Black 2 A Fletcher T Cook S Parker B Wira L Brown. Adelaide: S Welsh 3 B Burton 3 I Perrie 2 D Jarman A McLeod M Ricciuto.
Best: Fremantle: P Bell A Fletcher H Black J Longmuir B Cunningham A McPhee. Adelaide: A McLeod B Burton S Welsh S Goodwin B Hart K McGregor.
Injuries: Fremantle: Nil. Adelaide: N Bassett (corked thigh), S Goodwin (sprained ankle).
Reports: Nil.
Umpires: D Corcoran, D Morris, M McKenzie.
Official crowd: 19,535 at Subiaco
