Marlon King’s hat-trick earned Blues a courageous point after they fell 3-0 behind at The Den.
A pulsating affair in the capital started badly for the Blues as former marksman Chris Wood helped himself to a brace either side of Millwall’s second via Chris Taylor.
The match looked all but over after 20 minutes but Birmingham – and more specifically King – sparked into life either side of the interval.
When King equalised on 63 minutes Blues appeared favourites for victory, but they couldn’t quite find a winner after hauling themselves level.
The madness began on eleven minutes when Wood came back to haunt his former employers with a stooped header from two-yards out.
A long Millwall throw found its way into the area and Darius Henderson’s flick on left Wood with an easy finish.
And before Lee Clark’s side could catch their breath they slipped further behind, with Taylor drilling the ball into the roof of the net after Paul Robinson failed to deal with the cross in.
The hosts rounded off a ruthless spell courtesy of Wood lifting the ball over Steven Caldwell on the line, after a mix up in the visitors defence.
As the first-half wore on Birmingham found it increasingly difficult to get back into the game, especially when Jack Butland was forced to save Wood’s strike to prevent Millwall from moving 4-0 ahead.
But King did create a glimmer of hope for his side, however, when guiding home Leroy Lita’s sliced shot in stoppage time.
Although if it wasn’t for Butland’s flying stop keeping out Henderson’s ferocious drive, then Kenny Jackett’s men would have been out of sight moments after the break.
But shortly afterwards the comeback was very much on, as the brilliant King thumped the ball past Forde on the turn. This all came about due to Blues finally finding their feet and playing some intricate one-touch football in the build-up, resulting in David Murphy crossing to King.
Incredible scenes were to follow just after the hour mark; with King slotting Murphy’s cut-back past Forde after Ravel Morrison’s trickery started the move.
And Nathan Redmond almost edged Blues dramatically ahead as Forde had to be at his very best to save the youngster’s fierce effort.
Redmond and his team-mates did all they could to push on and bag an unlikely three points, though, it was Millwall who looked the more likely to score a fourth. Thankfully, Blues’ back line survived a barrage of pressure in the closing minutes to secure their 13th point of the season.
Millwall (in numerical order): David Forde, Alan Dunne, Danny Shittu (C), Liam Trotter, Darius Henderson, Liam Feeney (Andy Keogh 66), Mark Beevers, Chris Taylor, Jack Smith (Shane Lowry 46), Jimmy Abdou, Chris Wood.
Subs (in numerical order): Maik Taylor, Josh Wright, Karleigh Osborne, Scott Malone, Dany N’Guessan.
Goals: Wood (11, 19), Taylor (13)
Bookings: Lowry (79)
Blues: Jack Butland, Paul Robinson, Steven Caldwell (C), Curtis Davies, David Murphy, Wade Elliott, Ravel Morrison, Hayden Mullins, Nathan Redmond (Chris Burke 87), Leroy Lita, Marlon King.
Subs not used: Colin Doyle, Mitch Hancox, Will Packwood, Papa Bouba Diop, Darren Ambrose, Keith Fahey.
Goals: King (45+1, 49, 63)
Bookings: Mullins (41), Elliott (81)
Referee: Mark Haywood
Attendance: 9, 258 (510 Blues fans)