Jay Simpson was in seventh heaven after breaking a seven-game duck to score his seventh goal of the season with a priceless winner at Victoria Park.
On an afternoon in which The Lions simply could not afford to lose in their battle to beat the drop, Kenny Jackett's men came up trumps with a big, brave performance that reaped a thoroughly deserved reward of three points.
The injury jinx that has been a massive hinderance all season struck again before kick-off when defender Andy Frampton was ruled out after picking up a knock in training on Friday.
In stepped Marcus Bignot to fill the left-back berth, whilst Jem Karacan and Dave Martin came in for Ahmet Brkovic and Neil Harris, who both dropped to the bench.
After a quiet start the game sprung into life after 11 minutes when Simpson settled the vistors' nerves with a sublime flicked finish with the outside of his right boot from Karacan's delicious cross.
And the pacey teenager could have made it 2-0 barely 60 seconds later when Karacan found Simpson in space on the edge of the area. Unfortunately this time he slightly snatched at the chance and shot straight at home keeper Arran Lee-Barrett.
Much to the frustration of the home fans, Hartlepool played very much like a team whose season was effectively over, with a comfortable mid-table position already secure.
It was The Lions who looked hungrier, sharper and more positive in their approach as the first half progressed.
A deep Danny Senda delivery was well held by Lee-Barrett, who then reacted quickly to thwart the danger by grabbing the ball at Simpson's feet after another penetrating Karacan pass.
On 28 minutes it was Simpson's turn to try and set up Karacan with a slide-pass, only for Lee-Barrett to again be alert to the danger.
Two minutes later Andy Monkhouse did have the ball in the back of the Millwall net, but the linesman had already flagged to indicate that the player was off-side by a good two yards before despatching a low finish.
Back came Millwall and Martin was inches away from adding a second goal four minutes before the break with a rasping effort that smashed the crossbar before Michael Nelson headed the rebound over for a corner.
Hartlepool boss Danny Wilson had stated before the game that he wanted his players to approach their last four games with purpose and pride, and his side finally looked to heed his request with an improved start to the second half.
Ritchie Humphreys, on for Robbie Elliott, drilled a low shot wide from 18 yards and then Joel Porter's looping header flew over as the home team briefly threatened.
But The Lions defence, superbly marshalled by Paul Robinson, ensured that keeper Rhys Evans received excellent protection and ended the match without being really worked at all.
In fact it was Jackett's men, roared on by 323 magnificent fans at the Rink End of the ground, who could have added more goals.
Senda blazed a freekick high and wide and then Simspon, the game's outstanding attacking player, saw his 87th minute angled effort swerve agonisingly away from the far post as just as it looked to be creeping in.
Bas Savage, who ran his socks off throughout, saw his appeals for a penalty waved away by referee Rob Shoebridge after Willie Boland tripped him in the first of three nail-biting minutes of injury time.
Hartlepool mustered only their second corner of the match in the dying seconds, but once again were unable to cause any problems as Millwall stood firm for a victory that now opens up a five point gap on fourth from bottom Gillingham and drags Yeovil and Cheltenham right into the mire.
At the final whistle the players had a group hug, threw their yellow away shirts into the away end to show their appreciation and headed back south full of smiles.
None more so than skipper Robinson, who avoided a booking the day before the cut-off point that would have seen him miss both the Leeds and Cheltenham games if he had been yellow-card at Victoria Park.
The Lions are by no means safe, but for tonight at least, there is plenty to celebrate.

Hartlepool United: Lee-Barrett, McCunnie, Clark, Nelson, Elliott (Humphreys, 46mins), Sweeney, Boland, Monkhouse, Robson (Foley, 63mins), Brown (Mackay, 70mins), Porter. Subs not used: Budtz, Antwi.

Millwall: Evans, Senda, Bignot, Fuseini, Robinson, Craig, Martin (Smith, 57mins), Laird (Brkovic, 83mins), Savage, Simpson, Karacan. Subs not used: Edwards, Harris, Shaw.
Scorer: Simpson (11mins)

Ref: Rob Shoebridge
Att: 4,077 (away 319)