The Republic of Ireland international's 45 minutes to forget began with the game's opening goal when the Reading defender diverted Peter Whittingham's inswinging corner past his own goalkeeper (pictured).
And seconds before the break the centre-back saw red when he fouled former Royal Adam Le Fondre inside the box, allowing Whittingham to fire home the second from the penalty spot.
A late mistake from David Marshall allowed Michael Hector to net what turned out to be just a consolation for Nigel Adkins' men, who remain without an away win since August.
After an afternoon that saw their owner Vincent Tan and former manager Malky Mackay back in the headlines for all the wrong reasons, the spotlight turned to Cardiff's current incumbent Russell Slade as he looked to preserve his unbeaten home record since taking charge of the Bluebirds.
Slade's unchanged line-up had little of the ball in the opening 20 minutes, with Le Fondre's wayward header all they had to show for their endeavours.
That was until Reading skipper Chris Gunter, back at his boyhood club, was forced to put Craig Noone's inviting 19th-minute cross behind for a corner and Whittingham's back-post delivery was put past his own goalkeeper by Pearce.
Despite being behind Reading continued to look bright going forward against a Cardiff defence that had kept just two clean sheets all season, with Jordan Obita forcing Marshall into a stop at his near post.But in first half added time centre-back Pearce's miserable evening was compounded with just the second sending-off of his career
A lovely raking ball from John Brayford from the left-back position fed Le Fondre and when his former team-mate hauled him down inside the box, referee James Linington produced the red card despite protestations from Gunter that Pearce was not the last man.
Whittingham stepped up and sent Adam Federici the wrong way from the spot as Cardiff cruised into the interval.The Bluebirds picked up where they left off after the break with Federico Macheda forcing Federici into a diving save before wingers Anthony Pilkington and Craig Noone both fired over.
Having earned the penalty, Le Fondre was close to getting on the scoresheet himself against the club where he spent three years only for his optimistic chip to drop just the wrong side of the far post 12 minutes into the second half.
The home support were then up on their feet for the introduction of the popular playmaker Mats Daehli for just his second appearance since Slade's arrival.
But as the game ticked into the final 10 minutes they were sitting a little less comfortably after an error from Marshall allowed the 10 men a route back into the match
The ball pinged around the box before defender Hector's drilled effort from inside the box squirmed under the Scotland international to leave the vocal away following dreaming of the most unlikely of comebacks.
But the nearest Reading came to earning a late point was a penalty appeal for a foul on substitute Nick Blackman, only for Linington to show the forward a yellow card for diving.