On-the-whistle report: Ipswich Town 1 Rotherham United 0
The Millers dominated the second half at Portman Road but couldn't reply to a 31st-minute opener from one of the Tractor Boys' five January signings so far, Will Keane.
Defeat sees them remain in 21st spot, a place and two points above the bottom three.
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Hide AdIn an opening period of few opportunities, Millers goalkeeper Marek Rodak's first real job was to pick the ball out of the net just after the half-hour mark as Keane got lucky with a miscue and drove the ball home at the second attempt.
Rotherham should have gone in at the break level but Jon Taylor, having been left all alone with time and space by Anthony Forde's cross, volleyed a golden chance over the bar on the stroke of half-time.
Paul Warne's men came out firing in the second half but failed to take advantage of wave after wave of attacks.
Will Vaulks saw a long-range free-kick parried by Town keeper Dean Gerken in the 53rd minute while Michael Smith should have done better than head over from six yards following great Millers build-up play seven minutes later.
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Hide AdVaulks brought another save from Gerken late on and Joe Mattock was just beaten to the ball by Gerken but, with Rotherham's final ball lacking a cutting edge, the nervy home side held on for their third win of the campaign.
A bright spot on a poor day for the Millers was the performance of teenage midfielder Ben Wiles who excelled again in only his third league start.
Ipswich (3-4-3): Dean Gerken; Matthew Pennington, Luke Chambers, James Collins; Jack Lankester, Trevoh Chalobah, Cole Skuse, Callum Elder; Will Keane, Collin Quaner, Freddie Sears. Unused: Bartosz Bialkowski, Ellis Harrison, Teddy Bishop, Emyr Huws.
Subs: Flynn Downes (for Quaner, 65 minutes), Simon Dawkins (for Lankester, 74), Toto Nsiala (for Sears, 90+1).
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Hide AdRotherham (4-1-4-1): Marek Rodak; Zak Vyner, Sean Raggett, Clark Robertson, Joe Mattock; Semi Ajayi, Anthony Forde, Will Vaulks, Ben Wiles, Jon Taylor; Michael Smith. Unused: Lewis Price, Billy Jones, Michael Ihiekwe, Matt Palmer.
Subs: Ryan Williams (for Raggett, 37), Jerry Yates (for Forde, 70), Richard Wood (for Vyner, 89).
Goals: Keane 31 (Ipswich).
Referee: James Linington (Newport).
Attendance: 20,893 (729).