Thomas Waddingham was the Pompey hero with a late winner to fire them into the play-off positions - for now.
Introduced off the bench following his latest injury comeback, the Australian netted an 82nd-minute winner after Jake Cooper’s clearance deflected off him.
Earlier the Blues came back from 1-0 down after Nicolas Schmid’s awful kick presented Jenson Metcalfe with a sixth-minute lead.
That was cancelled out by Lyndon Dykes’ own goal following an Adrian Segecic free-kick - and then Waddingham claimed a 2-1 success to move the Blues into eighth.
And here are our Pompey player ratings...
13. Portsmouth midfielder Marlon Pack (7) during the EFL Championship match between Portsmouth and Millwall at Fratton Park Stadium, Portsmouth, England on 24th October 2026
Marlon Pack in the thick of the action against Millwall. Picture: Jason Brown | Jason Brown
14. Ebou Adams - 7
(Replaced Adrian Segecic on 61 mins) Another brilliant display off the bench, ensuring Pompey were on the front foot until the final whistle. | Jason Brown
15. Tyrese Shade - 7
(Replaced Ryan Kavuma-McQueen on 61 mins) Gave late energy to the Blues off the left flank and was involved in Waddingham's winner. | Jason Brown
16. Thomas Waddingham - 8
(Replaced Marko Milovanovic on 71 mins) What a fairy-tale return. The winner and a huge impact off the bench. | Jason Brown