The Lions needed a win to be certain of staying in the division while victory for out-of-form Palace would have made sure they were still in with a shout of escaping it.
But both sides drew a blank in an edgy derby encounter desperately lacking in quality.
It means Millwall are still hovering too close to the drop zone for comfort ahead of Saturday's tricky trip to Derby while the Eagles could yet slip out of the play-offs if they fail to beat Peterborough.
With so much at stake both sides were nervous from the kick-off but Millwall, on the back of three straight defeats, eventually settled down first.
Sean St Ledger volleyed wide and Andy Keogh just failed to connect with Liam Feeney's cross before Shaun Batt's shot from a quickly-taken corner was hacked clear by Danny Gabbidon.
Their best opportunity of the first half came when Keogh pulled the ball back to the edge of the area, from where Josh Wright curled inches over the crossbar.
Palace's early-season confidence has evaporated during a nine-game winless run and Wilfried Zaha, so often their key performer, showed his frustration by kicking out at Alan Dunne.
The Manchester United-bound winger escaped with a telling-off from referee Graham Salisbury and then set up the Eagles' first decent chance.
His low, driven cross was met by Glenn Murray six yards out but, with Danny Shittu breathing down his neck, the 30-goal striker's effort bounced wide.
Just before the break Owen Garvan's chip put Murray through on goal but Lions goalkeeper David Forde was off his line quickly to block.
They were the sort of chances Murray would have buried a couple of months ago but the Championship's top scorer has not found the net in his last eight matches and it showed.
After the break another Feeney cross shaved the head of Batt and Keogh could not control the rebound, before Julian Speroni sprawled at the feet of Batt to deny the lanky striker.
Palace's Yannick Bolasie almost conjured up a rare moment of magic with a 25-yard drive which was arrowing its way towards the top corner but Forde made a fine diving save.
Dunne and Zaha's bickering eventually got too much for Salisbury, who showed both yellow cards.
But no one was able to come up the goal which would have meant so much to one of these sides, meaning another nervy day in south London awaits at the weekend.
- Sports & Recreation
- Andy Keogh
- Shaun Batt
- Glenn Murray