Cardiff grabbed their third consecutive win at Boundary Park to get their promotion campaign off to the perfect start.
The Bluebirds had to work much harder than in last season's 7-1 romp but goals from Andy Campbell and Robert Earnshaw were enough to see off Oldham.
Home manager Iain Dowie was withought nine players through injury or suspension but he refused to blame the absences for defeat in his first game incharge.
Oldham had plenty of possession but the cutting edge belonged to a Cardiff team who lost in the semi-finals of last term's promotion play-offs.
Cardiff Boss Lennie Lawrence said: "It doesn't matter how much you are favourites to win a division, you still have to get off the mark.
"Oldham started each half well but after that we passed the ball and were quite comfortable in the end."
Dowie added: "I'm disappointed but Cardiff have outstanding players and we gave them a tough time.
We dominated the second half and just needed to get on the end of some excellent delivery."
Oldham started brightly and went close through Matty Appleby but Campbell opened his account in the 21st minute.
A right-wing corner was knocked on by debutant Chris Barker and Campbell - scorer of a superb hat-trick against the Latics last season - swivelled six yards out to apply a sweet finish.
Oldham had most of the possession but the visitors were strong in defence, with Barker and Danny Gabbidon in outstanding form.
They were happy to play on the break and after 84 minutes Earnshaw sealed the points.
Graham Kavanagh centred from the right, goalkeeper Les Pogliacomi didn't gather cleanly and sub Earnshaw tapped in from close range.
Oldham got their consolation in stoppage time as visiting keeper Neil Alexander also dropped a cross for Lee Duxbury to score from six yards out