The home side were the dominant force in the opening 45 but Cardiff had the first chance when Mark Hudson was left unmarked at a free kick but couldn't divert goalwards.
Daryl Murphy's header from two yards then bounced onto the frame of the goal before Campbell put Ipswich ahead in stoppage time at the end of the first half.
Lee Martin cut in from the left and floated over a cross that evaded everyone before striking Campbell clearly on the hand but he was not penalised.
Paul Jewell's men had the chance to double the lead 10 minutes into the second period but Emmanuel-Thomas blazed over after beating the Cardiff defence.
High-flying Cardiff began to turn the screw midway through the second period and they found an equaliser when Ipswich keeper Scott Loach spilled a cross and Helguson poked home from a yard.
Helguson scored the winner three minutes from time by meeting a deep cross unmarked at the back post.
He then almost handed Ipswich a late equaliser by inadvertently heading against his crossbar.
Cardiff go back to the top of the Championship while Ipswich stay rooted in the bottom three.