On-loan Hull striker Will Keane, making his Tractor Boys league debut, netted the winner in the 31st minute to take Town to within seven points of safety.
Rotherham remain fourth bottom, just two points above the relegation zone.
Ipswich boss Paul Lambert included new signings James Collins, Callum Elder, Will Keane and Collin Quaner in his starting line-up.
Quaner, on loan from Huddersfield, was adjudged to have fouled Rotherham keeper Marek Rodak when he chased down a back-pass early on.
Rotherham defender Zak Vyner received the first booking of the game in the 13th minute following a foul on Freddie Sears as Ipswich mounted sustained attacks on the United goal.
The hosts had appeals for a penalty turned down by referee James Linington when the ball appeared to strike the hand of Rotherham defender Sean Raggett.
Ipswich went ahead when Keane slammed home the winner from inside the six-yard box after his initial attempt was blocked following a cross from the left by Sears.
Just before the end of the first period a free-kick midway into the Ipswich half by Anthony Forde found Semi Ajayi, who headed narrowly wide.
Sears then shot just over the crossbar following a corner which was headed back across goal by Ipswich captain Luke Chambers.
Jon Taylor fired wide of Dean Gerken's left-hand post and five minutes into the second half a shot from outside the penalty area by Michael Smith was parried away by the Ipswich goalkeeper.
Rotherham were creating pressure on the Ipswich goal and a long-range shot from Will Vaulks was pushed to safety by Gerken.
And in the 60th minute Rotherham striker Smith's header went just over the bar as the away side began to dominate proceedings.
A flowing move down the left involving Trevoh Chalobah and Sears nearly led to the latter playing in Keane who was on his own just outside the visitors' penalty area.
Gerken had to get down to hold another shot by Vaulks in the 85th minute and in a frenetic period of additional time Gerken parried a deflection from defender Collins.
Rotherham manager Paul Warne felt his side gave him everything in a second period which they dominated.
He said: “It’s just how football is. I asked the lads to give me everything they’ve got.
“We did not cause enough problems first half, although we had a good chance to score, it’s difficult when you come away in the Championship.
“I thought we played really well and I’ve got no complaint of the lads performance at all.
“We needed a bit of quality on a couple of occasions but generally they were pretty outstanding and should be proud of what they try to do for us but unfortunately today it wasn’t enough.
“I think they only had one shot on target and I don’t think my keeper in the second half used his hands once and I think it was literally one-way traffic and I don’t think anyone, if we would have at least got a draw, would have any complaints, it just didn’t drop to us and it just wasn’t to be.”
Ipswich gave league debuts to veteran centre-back Collins, defender Callum Elder and strikers Keane and Collin Quaner who all signed in the January transfer window.
Keane slammed home his goal from inside the six-yard box after he miscontrolled his initial touch of the ball following a cross from the left by Freddie Sears.
But in the second half Rotherham dominated the game and should have at least come away with a share of the spoils with Ipswich keeper Dean Gerken and his back four managing to defend their goal.