With their top-eight spot in jeopardy and two key defenders out injured, the Magpies came from behind and survived three final-term lead changes to win 17.7 (109) to 15.11 (101).
In a highly entertaining game, the Pies had to contend with the tall Eagles' forward structure without Nathan Brown and Jack Frost for most of the game.
Vote for your top three players from Collingwood's gutsy eight-point win in the Magpie Army Player of the Year Award.
Brown sadly re-dislocated his right shoulder in the first quarter – the one he popped in round two against the Sydney Swans – while Frost was concussed and didn't play after half time.
Brown was taken to hospital and the Pies will now need to decide if he undergoes a season-ending reconstruction.
But the performance of Alan Toovey against Jack Darling and Tyson Goldsack versus Josh Kennedy was superb, with Nick Maxwell providing excellent support in a loose role and against the resting ruckmen.
The Eagles' defence was also commendable with Travis Cloke again ineffective and well held by Eric Mackenzie, and Darren Glass and Mitch Brown also influential.
It was by no means a complete win by the Magpies with coach Nathan Buckley critical of the fact they gave up 66 inside-50s, among other things.
But he was pleased with the resilience the team has shown it can build, and the growing belief and solidarity within.
"We just ground it out," Buckley said.
"It was a great win in the end, it wasn't a pretty win and it wasn't by design - we wouldn't have planned it that way during the week.
"But we were encouraged by the fact that the players just dug deep and got it done."
Dayne Beams, in his 100th game, was important in the third quarter when the game could have been taken by the Eagles.
Beams had 10 possessions in that term alone, with captain Scott Pendlebury collecting nine.
After trailing by 14 points at half time and being smashed 154 to 94 in uncontested possessions, the Pies had just two less touches in the third.
The Eagles had been well serviced by the first-half efforts of Matt Priddis, Matt Rosa, Andrew Gaff and Brad Sheppard, but in the third, it was the black and white ball-winners that had significant influence.
After Alex Fasolo and Steele Sidebottom kicked the last goals of the term, the margin was just six points at the final change.
Fasolo, in his first game since ANZAC Day, was having a say in the forward line while Jamie Elliot saved his first goal to reclaim the lead five minutes in.
The small forward, with his head bandaged, kicked another important major later in the term.
After Pendlebury put the lead out by another goal, Dean Cox tapped to Jamie Cripps and assisted in his major before marking strongly and following up with another.
A 50m penalty from Mitch Brown that put Brodie Grundy in the goal square was deflating for the visitors in red time, and when Cloke kicked his first and only with three minutes left, the Pies were home.
West Coast coach Adam Simpson conceded the Eagles simply couldn't hold on in the final 15 minutes and didn't deserve to win it.
"We're happy that we're seeing signs of improvement," Simpson said.
"We're definitely seeing some good signs. I thought our midfield as a collective stood up for the most part of the day.
"We had 66 inside-50s, so the supply was there, we just couldn't capitalise. Their defenders were actually really good."
West Coast's Brown spent time off the field in the first half after copping an off-the-ball torso blow from Jarryd Blair.
While Blair celebrated with a goal directly after, he might not be as happy once the match review panel examines the contact.
And, Elliot Yeo finished with one goal but two less teeth than he started the game with after colliding with Jarrod Witts seconds before half time.
The roots of the teeth remain so the former Brisbane Lion will have them capped in the coming days.
Collingwood 5.0 7.3 11.4 17.7 (109)
West Coast 5.2 9.5 11.10 15.11 (101)
Goals - Collingwood: Blair 3, Beams 2, Elliott 2, White, Goldsack, Witts, Macaffer, Ball, Fasolo, Sidebottom, Pendlebury, Grundy, Cloke
West Coast: Cripps 3, Priddis 2, Hill 2, Cox 2, Hurn 2, Yeo, Wellingham, Kennedy, Darling
Best - Collingwood: Beams, Sidebottom, Pendlebury, Blair, Swan, Lumumba, Macaffer
West Coast: Priddis, Selwood, Gaff, Hurn, Mackenzie, Naitanui, Cripps
Injuries - Collingwood: Nathan Brown (dislocated shoulder) substituted at quarter-time, Jack Frost (concussion)
West Coast: Nil
Substitutes - Collingwood: Clinton Young replaced Nathan Brown (dislocated shoulder) at quarter-time
West Coast: Mark Hutchings replaced Brad Sheppard in the fourth quarter
Reports: Nil
Umpires: Rosebury, Kamolins, Harris
Official crowd: 53,049 at the MCG
