The Lions avoided a third defeat in a row by stifling an in-form Forest side whose automatic promotion prospects took a slight knock.
The match started in a cauldron of noise at The New Den and it was the hosts who started the brighter.
Hameur Bouazza's direct running caused problems and he lashed a fierce effort just over the bar inside the opening 10 minutes.
At the other end, Lewis McGugan forced a finger-tips save from David Forde with a well-struck effort from outside the box.
Neil Harris was made aware of Wes Morgan's presence when the muscular defender barged into him from behind, but the Lions wasted the resulting free kick.
Forest went close in the 23rd minute when Chris Gunter drilled in a low cross which was just out of the reach of Joel Lynch at the back post.
Set-piece specialist McGugan tried his luck with a long-range free kick which flattened Darren Purse and deflected away to safety.
There was a brief moment of panic in the visitors' defence just before the break as James Henry tried to latch onto Harris' flick header, but Morgan made a timely intervention.
With Millwall's leading scorer Steve Morison struggling to make an impact up front, he was forced into defensive action when he cleared McGugan's threatening corner.
Much of the promise of the first half begun to fade after the break as both defences asserted their authority on proceedings.
The lively McGugan tried to get his side going again when he delivered a testing ball which flicked off the head of substitute Gareth McCleary, but Forde reacted well to turn the ball behind.
Millwall were on the back foot again soon after but demonstrated their defensive resilience when Purse cleared Chris Cohen's right-wing corner.
Robert Earnshaw was introduced late on with Billy Davies urging his side forward in search of their 10th win in 14 matches.
The Welshman was inches away from linking up with McGugan, whose lay-off fell just out of reach of the dangerous striker.
Henry fluffed his lines when well placed to provide a cross for Kevin Lisbie, with his delivery floating harmlessly out of play.
But it was Forest who finished in the ascendancy with a string of set pieces which threatened to unsettle the hosts, but they held their nerve.
Both sides had to settle for a point, just as they did in the reverse fixture, but the Lions now have their work cut out to make the play-offs.
Forest, meanwhile, still have their sights set on a top-two finish but will need to show more prowess in front of goal if they are to achieve their aim.