The Newcastle striker has scored six times during the current qualifying campaign, and set up the only goal of the night against Georgia in the all-important final group match.
Mitrovic - who played for 77 minutes - crossed for Aleksandar Prijovic with 16 minutes remaining to ensure that Serbia topped Group D.
That sparked scenes of jubilation at the Stadion Rajko Mitic, with Mitrovic unsurprisingly at the heart of the celebrations.Elsewhere in the same group, Wales and Republic of Ireland met in Cardiff and both sides knew that they could secure automatic qualification if Serbia slipped up.
Ciaran Clark started for Eire while Rob Elliot was on the bench, and a James McClean strike in the second half broke Welsh hearts. Ireland, meanwhile, will go into the play-offs.