The Lions have left it too late to reach the play-offs, but to their credit battled well and claimed a win to leave The Rams still looking for the points which will secure their Division One status.
Neil Harris netted an early opener for the visitors, after Derby keeper Andy Oakes, who later went off injured, dropped a routine cross.
Giorgi Kinkladze fashioned an equaliser on eight minutes when wriggling through and firing home.
Both sides had chances, with Fabrizio Ravanelli shooting tamely for The Rams and Harris firing an effort wide when clean through for Millwall.
An error on 63 minutes by the Derby defence allowed Mark McCammon to race clear before going past the keeper and netting the winner for Millwall.
Click below for match stats:
Division One
Derby 1-2 Millwall
Click here for an updated Division One table.
