The striker, who spent the first half of the season on loan at Portman Road, lashed home from close range after the visitors failed to clear a corner.

Matt Derbyshire's earlier header put the Millers ahead as he stooped at the far post following a defensive lapse.

Rotherham goalkeeper Adam Collin made several saves, including a fingertip stop from Luke Chambers' header.

The three points for Steve Evans's men was just their second victory at the New York Stadium since mid-October, while Ipswich have now won once in their last six league games and drop to fifth in the table.

Daryl Murphy, the Championship's leading scorer with 18 goals, spurned a glorious opportunity to put the visitors ahead after just 16 seconds when he burst into the box after outmuscling Millers captain Craig Morgan, but his weak effort was saved easily by the legs of Collin.

After such a bright opening, the game quietened down before the hosts opened the scoring through former Olympiacos forward Derbyshire.

Ben Pringle's deep free-kick evaded every Ipswich player, Morgan flicked the ball on and it found its way to Derbyshire, who bravely dived in to nod home.

The visitors began the second half brightly and almost equalised when Cole Skuse's pin-point free-kick found the head of Chambers, but his powerful header was superbly tipped over by Collin.

Shortly after Murphy's header was cleared off the line by Zeki Fryers, the hosts went down the other end and doubled their advantage through Derby loanee Sammon.

Pringle's corner was not cleared by the Tractor Boys' defence, the ball broke to Sammon and he lashed it past Polish keeper Bartosz Bialkowski.

The second goal seemed to deflate Mick McCarthy's side as they pushed forward but failed to create any clear-cut opportunities before Millers substitute Jordan Bowery almost made it 3-0 in stoppage time, when he raced through on goal but his attempt was kept out by Bialkowski.

Rotherham manager Steve Evans:

"I think it was a wonderful performance, full of all the things that we're good at. We were good on the ball, good in possession and there was fantastic industry from everyone in a Millers shirt.

"We have beaten an excellent side. They should probably have been one up in a minute. We took 15 minutes to settle ourselves down. We had to grind it out. My players deserve enormous credit.

"I think Conor Sammon does a lot of things in the game that perhaps not everyone sees. His willingness to work hard really is an asset."

Ipswich manager Mick McCarthy:

"I thought Rotherham played well. The game is going nowhere and they score from the free-kick which was poor marking from us and not like us. There was nothing special or strange about the deliveries - we should have dealt with them better.

"When we conceded the second goal it was actually after our best spell. We've had chances but if we defend like that then it will cost us.

"I might have to look at freshening it up with the players I've got and keep going."

BBC Sport