Replacements: Max Abbott, Gavin Duffy, Cathal O'Flaherty, Luke Cahill, Chris Quinn.
Replacements: Ed Rossiter, Sean Seymour, Mark Hanrahan, Alex Wootton, Geoff Ryan.
Cork Con had the benefit of the blustery conditions in the opening half, with a heavy wind and rain behind them, but despite establishing territorial dominance Garryowen's defence proved impregnable.
Johnny Holland put the Leesiders ahead in the 11th minute and the Limerick side had to bide their time before hitting back on the half hour mark, with Munster's Barry O'Mahony touching down from a ruck close to the Constitution line.
The try went unconverted and Holland hit back for Cork Con before half-time, handing them a 6-5 advantage thanks to a well-struck 37th minute penalty.
However, Garryowen stormed out of the blocks in the second period with a Jamie Gavin penalty immediately restoring their narrow lead.
The visitors pressed for a try and got their reward when young winger Harry McNulty scored for the second week running, with Gavin supplying the extras in the 48th minute.
But Constitution were back at their clinical best in the remaining half hour as they engineered tries for in-form flanker James Ryan, who now has three to his name for the campaign, and prop Bryan Cagney.
A turning point occurred in the 53rd minute with the sin-binning of Garryowen second row Aaron McCloskey. The resultant play yielded Ryan's score, and Holland's conversion left Constitution just two points behind (15-13).
Gavin missed a penalty chance in the 61st minute for Garryowen. Then play was held up in the 68th minute for an injury to a Garryowen player, with Cork Con in a promising attacking position.
A similar attack in the 79th minute, however, yielded the winning points as Cagney finished a series of mauls with an unconverted try.
Garryowen fully deserved their losing bonus point to get their season underway, and will surely add to this fine display in the weeks ahead.
For their part, Constitution will be glad to get the home win and can now look forward to the local derby against Dolphin next Friday evening, under the Musgrave Park floodlights.
Referee: Sean Gallagher (IRFU)