The Hatters started brightly and could have been three up within the first half an hour as Millwall's hesitant defending allowed the visitors to lay siege to their goal.
Rookie striker Ryan Charles was just off-target with an angled drive and then headed a David Bell cross straight at Lions keeper Rhys Evans.
But the best chance fell to veteran campaigner Don Hutchison in the 23rd minute. After skilfully chesting down a superb pass from Lewis Emanuel, the former Millwall man surged towards goal and unleashed a fierce drive that was parried away by Evans.
In the second half the Lions roared their way back into the game and Jay Simpson wriggled free of Emanuel's tight marking to carve out a chance just after the hour mark, but his touch let him down as he rounded Hatters keeper Dean Brill and the danger was cleared.
Bas Savage then headed onto the roof of the net from an Ahmet Brkovic cross as the Lions stepped up another gear and on 78 minutes former Hatter, Brkovic, almost stole the points when he smashed a left-foot shot against the underside of the bar from 12 yards out.
Another chance went begging five minutes from time when Brill could only palm Danny Senda's dangerous low cross into the path of Savage, but the big striker spooned over the bar with the goal at his mercy.
As the clock ticked away, there was still time for Savage to be denied again, this time Richard Jackson flung himself in front of a goalbound effort.