BARRY HAYLES' late, late show heaped misery on shell-shocked Preston just when it seemed they'd win their first game in four.
But Billy Davies' side only had themselves to blame after squandering a string of chances following Eddie Lewis' 15th-minute opener.
The game turned when Millwall's player-boss Dennis Wise, out with a calf injury, sent on Paul Ifill and Danny Dichio midway through the second half.
Within two minutes of Ifill's arrival Hayles fired the first warning with a drive that fizzed narrowly wide.
And as the game drew to a close, Millwall turned the screw even more as Hayles forced Preston keeper Jonathan Gould into a breathtaking reflex save and Ifill hit the post a minute later.
Millwall finally got their reward with an 87th-minute equaliser. Hayles was left with the easiest of headers as Gould landed in a heap following Dichio's challenge.
Last week David Healy bagged a brace for Leeds just days after leaving Deepdale.
This week Scott Dobie, lined up as a replacement for Healy, snubbed them, joined Millwall from West Brom for £500,000 and made his debut.
But Lewis gave Preston the start they needed early on when he intercepted Josh Simpson's poor pass and scurried infield to fire a low drive from the edge of the area tight into the corner of Graham Stack's net.
Richard Cresswell missed two good chances for Preston and had a strong penalty appeal denied in first-half injury time when Kevin Muscat upended Lewis.
PRESTON: Gould 7 - Alexander 6, Mawene 6, Lucketti 6, Curtis 6 - Daley 5, McKenna 6, Etuhu 7, *LEWIS 8 - Cresswell 7, Lynch 5 (Langmead, 66min, 5).
MILLWALL: Stack 6 - Phillips 6, Lawrence 6, Ward 6 - Muscat 6 (Dichio, 74mins), Elliott 6, Tessem 5 (Ifill, 60mins, 7), Livermore 6, Simpson 5 - *HAYLES 8, Dobie 6.
Ref: B Curson 5.