Substitute Magaye Gueye snatched a point with an 88th-minute leveller for the Lions, who were outplayed in the first-half and trailed to goals from Steve Cook and Brett Pitman.
Manager Ian Holloway threw caution to the wind and played with five recognised strikers on the field for the last half-hour and midfielder Ed Upson sparked an unlikely comeback with a 75th-minute header.
Bournemouth had started the match in familiar attacking fashion and took a two-goal lead inside 25 minutes against a team who had won just one of their previous 13 games.
Manager Eddie Howe was without injured 11-goal top-scorer Callum Wilson and his replacement Pitman looked lively from the off as did Matt Ritchie, who twice threatened in the early stages.
The winger’s spectacular drive from 30 yards had Millwall goalkeeper David Forde, making his 300th appearance for the Lions, scrambling after 17 minutes.
The Cherries were rampant down the right flank with Ritchie and Simon Francis providing ammunition for Pitman and Yann Kermorgant, who met Francis’ cross but glanced his header just over the bar after 20 minutes.
Francis then supplied Pitman, whose downward header forced Forde to tip the ball over the bar, before Bournemouth broke through twice in quick succession.
Defender Cook nodded home at the back post from a simple Andrew Surman cross in the 22nd minute before Pitman swivelled onto Ritchie’s pass and guided the ball into the net three minutes later.
Millwall rarely threatened in the first half – Martyn Woolford proving their best attacking outlet – but it was all change after the break, as they probed with more intent and Woolford went close, glancing over a header from a Shaun Williams free-kick.
Defender Byron Webster twice threatened from set-pieces but his headers were routinely dealt with by Bournemouth goalkeeper Artur Boruc.
However, when Upson rose highest above a series of Cherries defenders to nod home Jermaine Easter’s cross with 15 minutes to play, the visitors sensed an opportunity and bombarded the hosts’ back-line for the final stages.
Boruc dropped the ball from a corner and then tipped over the bar from Fuller as Millwall pressed, but Bournemouth should have secured the points on the break only for Pitman and substitute Junior Stanislas to make a mess of it.
Still Millwall would not bow and when striker Lee Gregory’s shot was blocked Gueye drilled in the rebound with two minutes left to play.