Freddie Sears’s third goal of the season has given the Blues a 1-0 half-time lead over Bristol City at Portman Road.
Boss Paul Lambert named the same starting XI for the fourth successive match, while Ellis Harrison was back on the bench after his ankle injury having been out since the end of September.
Bristol City, who included former Blues central defender Adam Webster in their starting line-up, made two changes from the team which lost 2-0 to Leeds at the weekend.
Josh Brownhill was suspended having been red-carded in that game, while Jack Hunt dropped to the bench with Liam Walsh and Eros Pisano replacing them in the XI.
The Robins were the first to threaten as Town started slowly. In the fourth minute keeper Bartosz Bialkowski superbly tipped a Walsh shot from the edge of the box over the bar.
A minute later, Jamie Paterson cut in from the left after the Blues had made heavy weather of clearing but shot wide.
But Town quickly began to get themselves into the game and in the eighth minute Freddie Sears hit a shot from just outside the box which struck the stanchion to the right of Niki Maenpaa’s goal.
The Blues were beginning to make some headway, particularly down the right flank but with Gwion Edwards and Jordan Spence unable to find team-mates with their crosses.
On 12 managers Lambert and Lee Johnson engaged in a heated exchange after Jamie Paterson appeared to flick out at Edwards as they fell between the technical areas, the Welshman having fouled him. After a stern word to both managers the game continued without a card being issued.
The game continued to be an even affair with neither side creating an opportunity until the 21st minute when Andres Weimann was found in an offside position following a quick Bristol City break.
Four minutes later, Jordan Roberts, clearly frustrated that referee David Webb had failed to spot him being man-handled by the Robins centre-halves on a number of occasions, was booked for a late challenge on Tomas Kalas.
Just before the half hour, with referee Webb having continued to make decisions which irked the Town players and support - not least one tackle on Edwards that looked both high and late - spoke to Roberts again following an innocuous foul, presumably to tell him one more and he would be shown another card.
The Blues had begun to get on top as the half moved into its final quarter of an hour but without having created a serious chance.
But in the 32nd minute they took the lead. Former Robin Cole Skuse played a brilliant cross-field pass to Sears on the left and the striker drove into the area at pace before hitting a low shot across Maenpaa and into the corner of the net before celebrating his third goal of the Lambert era - as well as his 29th birthday yesterday - with his team-mates in front of the tunnel.
The Blues began the put the visitors under pressure. Roberts hit a 38th-minute freekick from just outside the area into the wall, then a minute later Trevoh Chalobah hooked over after a Jonas Knudsen long throw had bounced to him in the box, skipper Luke Chambers having won the ball in the air.
As the half moved into its final few minutes Bristol City briefly started to look the more threatening side but Town were able to repel them and were back on the front foot again as the half moved one additional minute.
Seconds before the whistle, all-action goalscorer Sears intercepted a ball laid back for a shot on the edge of the box then continued his run to the Robins left to prevent Lloyd Kelly from being able to get it back in the danger zone.
The whistle went soon afterwards with Town deserving their lead after an entertaining - if rather mistake-ridden - half.
The Blues had started poorly and City might well have taken the lead but for Bialkowski’s early stop but found their feet and had looked the more composed team when the goal came, even if chances hadn’t been coming in great numbers.
Town will hope to grab a second goal early on after the break to settle their nerves as they look to complete their first win of the Lambert era and their first at Portman Road since April.
Town: Bialkowski, Spence, Chambers (c), Pennington, Knudsen, Skuse, Chalobah, Downes, Edwards, Sears, Roberts. Subs: Gerken, Donacien, Jackson, Harrison, Bishop, Ward, Lankester.
Bristol City: Maenpaa, Kelly, Kalas, Webster, Adelakun, Eliasson, Walsh, Pack (c), Pisano, Paterson, Weimann. Subs: O’Leary, Dasilva, Baker, Diedhiou, Morrell, Hunt, Eisa. Referee: David Webb (Lancashire).