The match-winning strike from Ireland, which made it eight League wins in a row at Eastlands, came in the 94th minute after it looked as though City would be held by battling Reading.
But with virtually the last kick of the game, City lumped a long ball forward, which was headed on by Geovanni for Ireland to score with a spectacular volley into the top corner from the edge of the penalty area.
There was no repeat of the over-zealous celebrations when Ireland dropped his shorts after scoring the winner in the previous home game, against Sunderland.
It looked as though it was destined not to be City's day when, in stoppage time, Geovanni, clean through on goal, blasted over from ten yards, with only keeper Marcus Hahnemann to beat.
Reading had made the brighter start, though it was City who took an 11th minute lead through Martin Petrov.
A well-worked move saw Elano strike an upright, before Emile Mpenza's follow-up shot was blocked by Hahnemann. Bulgarian winger Petrov was on hand though to rifle home the rebound for his fourth goal of the season.
City produced some delightful, flowing football in the opening period, only to be let down by a lack of a cutting-edge in front of goal.
The Royals kept plugging away and were rewarded with an equaliser shortly before half-time.
Kevin Doyle and Bobby Convey linked up well to set up James Harper, who walloped home a shot into the top corner from the edge of the penalty area, a spectacular second goal of the season for the midfield player.
City were forced to make a change late in the first half when Vedran Corluka was injured, while at half-time Georgios Samaras replaced Mpenza. Just short of the hour Geovanni was brought on for the travel-weary Elano.
City huffed and puffed, but seldom looked like blowing their way through the Royals defence until the dramatic finish to the match.
Geovanni saw a long-range drive dip narrowly over the crossbar, while Samaras was denied by Hahnemann, who raced off his line to block the shot from the Greek striker.
But with time running out, midfield-man Ireland again showed he had the knack of scoring important goals as he found the net for a fourth time this season.