The former Burnley star grabbed the all-important equaliser to leave his former club alongside his current one, deep in relegation trouble.
Last season Mullin only managed three goals, but two of them came in a 6-2 win at Burnley!Robbie Blake ended a personal barren run of ten games without a goal when he fired the home side in front in the 35th minute.
There seemed little danger but when the ball broke free, Blake just took one touch before hitting home an unstoppable left-foot shot for his seventh goal of the season.
Rotherham seemed to be heading for defeat as Burnley took the game by the throat and should have wrapped it up when good chances fell the way of both Blake and Ian Moore, who was up against the team managed by his father Ronnie.
Burnley were made to pay in full for the missed chances when old boy Mullin burst down the middle to gather a pass from Paul Warne and sidefoot home a deserved equaliser.
Ironically, Mullin might have won it late on- for Burnley!His attempted clearance was heading towards his own goal before Rotherham keeper Gary Montgomery came to his rescue with a timely save.