Ipswich boss Paul Jewell opted to leave out striker Michael Chopra, who attracted headlines for all the wrong reasons on Thursday having been one of nine people charged in connection with race-fixing by the British Horseracing Authority.
His place in attack went to Campbell, who had joined on a three-month loan from QPR only on Friday, and the former Birmingham, Leicester and Blackpool frontman gave the home side a deserved lead when netting in first-half stoppage-time after the ball came off his hand amid confusion in the Cardiff defence.
But for all their dominance in the opening period, the Tractor Boys were not able to record their first home win of the season as the Championship strugglers conceded two soft goals from crosses as Helguson netted both, including the winner in the 88th minute.
Cardiff's Mark Hudson wasted a header from a free-kick early on, before the hosts went on to dominate the first half.
Fine link up play on the left resulted in Aaron Cresswell curling an inviting ball into the area but Campbell, at full stretch, was unable to steer the ball past on-rushing Bluebirds goalkeeper David Marshall and saw his effort go wide.
On 27 minutes, Jay Emmanuel-Thomas sent a powerful, low shot from all of 30 yards that swerved dramatically towards the bottom right corner and had Marshall at full stretch as he produced a brilliant finger-tip save.
Daryl Murphy then headed onto the base of the left-hand post from close range, before the Tractor Boys made their pressure count.
Lee Martin's dangerous cross from the left caused a mix up as Marshall and centre-half Matthew Connolly left the ball to each other and the ball hit the on-rushing Campbell and rolled into the empty net.
Replays clearly showed the ball hit the outstretched hand of Campbell and the 30-year-old immediately looked across at the assistant referee expecting to see a flag, but when it didn't arrive he ran away to celebrate a first goal as an Ipswich player.
Campbell received a standing ovation when he was brought off just before the hour mark to be replaced by Jason Scotland, but the break in play seemed to work in Cardiff's favour as they then started coming more into the game and levelled on 63 minutes.
Substitute Craig Conway looked to have wasted his crossing opportunity on the left as he floated his delivery too close to Loach, but the Ipswich shot-stopper was unable to cleanly gather and spilled the ball into the path of Helguson, who had the easiest of tap-ins.
Both teams enjoyed good spells of pressure following the goal, but it was Cardiff who started to look the more likely having taken the sting out of the game with their equaliser.
Andrew Taylor stung the fingers of Loach with a drilled effort from the left angle of the area, before Rudy Gestede's header deflected off for a Cardiff corner.
Malky Mackay's side grabbed all the points when Taylor's high cross into the area from the left caused more hesitation in the Ipswich defence as Cresswell left the ball thinking Roach was coming out to claim and Helguson leaped high at the far post to head home unchallenged with two minutes to go.