|Venue: City Ground
MILLWALL won for the first time in nine matches to give their survival hopes a major boost.
Substitute Ricardo Fuller capitalised on Stephen McLaughlin's defensive lapse to score the only goal of the game seven minutes from time.
Forest's best chance came midway through the second half when Britt Assombalonga headed goalwards and David Forde tipped the ball onto the bar.
But the visitors were good value for their victory and while the winner was the result of an error, it did not come against the run of play.
Millwall, who host Huddersfield Town at The Den next weekend, are now just two points behind fourth-bottom Brighton.
Ian Holloway made three changes following Tuesday's 0-0 draw with Reading – two of them enforced.
Dan Harding (ineligible) and Sid Nelson (suspended) were unavailable, with Mark Beevers and Alan Dunne replacing them, while Lee Martin came in for Lee Gregory.
With Paris Cowan-Hall also missing through injury, Holloway named young forward Aiden O'Brien on the substitutes' bench.
Stefan Maierhofer was preferred to Gregory in the lone striking role as Millwall reverted to a 4-2-3-1 formation.
Maierhofer almost got on the end of game's first chance but Kelvin Wilson made an important clearing header to divert Beevers' high cross away from the Austrian striker.
Beevers was on hand at the other end to block Henri Lansbury's drive, which looked to be heading on target until the defender flung himself in front of the ball.
In the 15th minute,Martin landed heavily on the touchline, injuring his ribs, and he was unable to continue despite receiving treatment.
The winger was replaced by Ed Upson, who took up a central midfield position with Diego Fabbrini moved from the no.10 role to the right flank.
A mix-up between Dunne and Shaun Cummings saw the latter's free-kick intercepted by Michail Antonio but his effort was kept out by David Forde.
Magaye Gueye thumped a half-volley wide, Fabbrini skipped past a tackle before his dangerous cross was cleared and Jos Hooiveld blasted over from distance during a spell of Millwall pressure.
And they went agonisingly close to breaking the deadlock in the 29th minute.
Upson won and took a free kick on the left-edge of the area and his inswinging delivery was met by Beevers, whose glancing header was tipped wide by Dorus de Vries.
de Vries' opposite number Forde was called into action moments later, eventually claiming Robert Tesche's header after a Forest corner bounced around inside Millwall's box.
Lansbury then curled a free kick onto the roof of the net but the Lions – inspired by Italian maestro Fabbrini – ended the first half on top.
He won a corner at the end of a mazy run before teeing up Beevers for a long-range drive, but his shot sailed harmlessly beyond de Vries' post.
Forest began the second half at a blistering pace, with Assombalonga and Robert Tesche hitting the woodwork twice in quick succession.
But Millwall rode the storm and slowly grew into the ascendancy.
Shaun Williams found Maierhofer with a clever chipped pass but the striker blazed over and then headed Magaye Gueye's cross wide before he was replaced by Gregory.
Millwall were more threatening with Gregory on the field and he did brilliantly to break into Forest's box and ride two challenges only to be thwarted as he went to pull the trigger.
The decisive moment came in the 83rd minute when McLaughlin misjudged a header back to de Vries, allowing Fuller to nip in and score from close range.
Dunne and Jos Hooiveld made a string of heroic clearances during four minutes of added time as the Lions closed out the match and claimed all three points.