Daniel Nardiello struck against his former side to help Rotherham ease to victory over promotion rivals Exeter.
The Millers made the perfect start when Ben Pringle seized upon a slack pass by the Grecians' Scot Bennett to fire his side ahead after only 64 seconds.
Nardiello doubled the lead after combining with Pringle, and Michael O'Connor's deflected shot made it 3-0.
Danny Coles got a scrappy consolation goal for the visitors after Craig Morgan smashed in Rotherham's fourth.
Morgan's first goal for the Millers added gloss to the result which sees Exeter - who have now lost their last four games - drop out of the League Two play-off places following Bradford's win over Bristol Rovers.
Meanwhile, Rotherham's comprehensive victory at the New York Stadium leaves them three points off the automatic promotion places in sixth.
VIEW FROM THE DRESSING ROOM
Rotherham United manager Steve Evans told BBC Radio Sheffield:
"When you come up against an excellent side with a lot of good players and an experienced manager, who I have the highest regard for - I thought tonight would be difficult.
"We got the early goal which I think unsettled them a bit.
"When we play like that and pass and move as we did in the first half its very difficult to limit us."