After only 30 seconds of Keane's first game in charge, Ipswich defender Alex Bruce had Richard Wright stretching for an over-hit back pass.
With 10 minutes gone, Ivan Campo brought down Roger Johnson in the area following another cross from the sprightly Chris Burke, but Ross McCormack's spot-kick was pushed away brilliantly by Richard Wright to deny City the lead their early play deserved.
Ipswich roared back and Pablo Counago should have done better at the far post as he ran in to meet a cross from Jaime Peters.
Town were forced to make a change in the 27th minute when Bruce left the field with an arm injury to be replaced by Jon Stead.
In the 34th minute, Ipswich took the lead when a long ball over the top saw Stead out-pace Gabor Gyepes and cross into the danger area where the unmarked Counago had the easy task of firing into the net.
The Bluebirds were knocked out of their stride by that goal and Town were well on top with their midfield running the game and the veteran Campo mopping up anything at the back.
Ipswich went two up in the 51st minute when the Cardiff defence failed to clear the ball far enough up the field and David Norris picked his spot to fire into the corner of the net from 20 yards.
Stephen McPhail and Michael Chopra went on in the 59th minute and Chopra almost burst through but a last-ditch tackle by Matt Richards cleared the danger.
The home side never looked like doing enough to draw the game, although substitute Eddie Johnson did force a fingertip save from Wright in the closing minutes.
The impressive Stead struck a third for the Tractor Boys in the 90th minute after a Campo free-kick had rebounded off an upright to secure all three points for Roy Keane on his bow as Town manager.
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