Both sides ended with ten men and both were awarded penalties, but while Bluebirds skipper Graham Kavanagh had his 29th minute spot-kick saved, Gary McSheffrey made no mistake in the 70th minute to give the Sky Blues a deserved victory.
"We defended brilliantly and coped with the loss of Peter Clarke so early on very well," said Coventry manager Eric Black.
"Our mentality was spot on and I said to my players at half-time that we could go on and win the game.
"We showed a fantastic attitude and that was the best we have played since I came to the club.
"It was a great team performance and I hope the players take confidence from it for the rest of the season." In an explosive start Coventry defender Clarke was dismissed after a two-footed lunge on John Robinson with just 25 seconds on the clock.
Cardiff failed to take advantage of their numerical superiority and when Kavanagh's spot-kick was saved it looked inevitable they would go on to struggle.
Julian Joachim began making runs into the Cardiff danger area and when he burst thorough in the 67th minute, Martyn Margetson brought him down to earn a red card and give the Sky Blues the spot kick that won the match.
Cardiff boss Lennie Lawrence was devastated by his team's performance. "It was embarrassing and inept and I feel sorry for the fans and sorry for the club," he said.
"We have to get some pride back quickly because the supporters and the club deserve that.
"We created very few chances and I can't recall any other game where we gave the ball away so easily.
"This is the worst night since I came to the club and I hope the players are as ashamed as I am with the performance.
"I was halfway up a hill before tonight and now after that I am back at the bottom."