Second-half goals from Jordan Shipley and Conor Chaplin ensured all three points for the Sky Blues.
City’s first goal came from Shipley’s strike, which with help from a John Mousinho deflection found its way beyond the wrong-footed Jonathan Mitchell.
Oxford had the chance to level the score-line straight from the restart but Lee Burge saved expertly to his right-hand side which denied James Henry.
Shipley caused further mayhem for the hosts as he was fouled by Mitchell in the penalty area to give City the opportunity to double their advantage.
New signing Chaplin stepped up to convert the spot-kick confidently into the middle of the net for his first goal in a City shirt.
Jon Obika pulled one back for the hosts late on but it wasn’t enough to form a late comeback.
An early chance came for United inside seven minutes with James Henry’s first-time strike bouncing off of the crossbar after Cameron Norman’s pull back.
City’s first opportunity fell to newboy Chaplin, the summer acquisition jinked his way into the box from Tom Bayliss’ through ball but his and Shipley’s follow up strikes were blocked by Curtis Nelson.
Luke Thomas’ sheer pace was utilised effectively in the first-half with a combination down the right-hand allowing the loanee to get a shot on goal from a tight angle, however his Derby County counterpart Mitchell saved well.
Michael Doyle’s free-kick was met by Jordan Willis just five minutes into the second-half, but the central defender was unable to direct the ball goal-wards.
Chaplin and Mousinho had a couple of attempts at goal midway through the final period, neither though took advantage of their chances.
The Sky Blues now sit in 12th place in the Sky Bet League One.
Yellows: Jordan Shipley, Junior Brown, Ricky Holmes, Clarke-Harris
Goals: Jordan Shipley, Conor Chaplin, Jon Obika
Sky Blues XI: Lee Burge (GK), Jack Grimmer (45), Jordan Willis, Dominic Hyam, Junior Brown, Michael Doyle (C), Tom Bayliss, Luke Thomas, Jordan Shipley (83), Conor Chaplin (83), Jonson Clarke-Harris.
Subs: Liam O’Brien (GK), Tom Davies, Dujon Sterling (45), Abu Ogogo (83), Tony Andreu (83), Amadou Bakayoko, Jordy Hiwula.
Oxford XI: Jonathan Mitchell (GK), Cameron Norman, Curtis Nelson (C), John Mousinho, Josh Ruffels, Shandon Baptiste (83), Cameron Brannagan, James Henry, Marcus Browne (71), Ricky Holmes, Jamie Mackie (83).
Subs: Scott Shearer (GK), Luke Garbutt (83), Rob Dickie, Sam Smith (83), Jon Obika (71), Sam Long, Fabio Lopes.