Replacements used: Frank Cogan (Clontarf) for Hogan (38 mins), Liam Og Murphy (Young Munster) for Walsh (48), Risteard Byrne (UCD) for Slattery, Hugh McGrath (Young Munster) for Condon (both 60), Barry Keeshan (Dolphin) for Ronaldson (70). Not used: Brian Slater (UCC), James Thompson (Ballynahinch).
Replacements used: Gary Holborn (Melrose) for Brown, Neil Dymock (Dundee HSFP) for Cox (both 50 mins), Richard Hawkins (Dundee HSFP) for Sutherland, Andrew Rose (Boroughmuir) for Dodds (both 55), Fraser Brown (Heriot’s) for Crombie, Morgan Ward (Aberdeen Grammar) for Black, Danny Gilmour (Stirling County) for Kelbrick (all 65).
Fraser Thomson, Sean Crombie and Rory McKay managed to cross the whitewash for the Scots as they set up a grandstand finish, but Rodger McBurney's try and some assured place-kicking from Craig Ronaldson confirmed the home win.
Lansdowne clubman Ronaldson landed three penalties and a conversion as new Irish head coach Conor Twomey watched his charges take the Ulster Bank Club International spoils.
The enthusiastic home supporters were treated to an excellent, high intensity encounter, and Ireland, in their first game of a two-match run, had all of the early pressure.
Cork Constitution winger Cathal Quinn, one of five debutants in the hosts' starting line-up, made an early break with Ronaldson and centre Killian Lett also involved, but the Scottish defence held firm in the fourth minute.
Scotland flanker Rob Colhoun charged forward on an impressive run but the visitors were penalised for a forward pass, and Ronaldson took the opportunity to kick Ireland ahead with a tenth minute penalty.
Ireland dominated possession over the next five minutes, but despite a string of passes and some good play from O'Mahony, Mike Kelliher and Cian Aherne, Scotland's solid defence held them at bay.
The visitors looked set to break the try-scoring deadlock when centre Dean Kelbrick cut through at the end of the first quarter, but a spilled pass from Ross Curle to Dougie Fife saw Ireland turn the ball over.
Just two minutes later, Ireland were celebrating their first try of the night. Lett and Aherne pressed hard in attack and despite plenty of bodies being present on the Scottish side, O'Mahony succeeded in sneaking through to give the hosts an 8-0 advantage.
Ronaldson's conversion attempt bounced back off a post and Scotland wasted little time in replying. There was some great interplay between Thomson and Callum Anderson before full-back Thomson crashed over for a well-worked score, converting a two-on-one overlap. Out-half Lee Millar kicked the two points to close the gap to the minimum.
Scotland, showing the benefits of a win over French opposition last week, controlled possession for the next five minutes, but home centre Kelliher did well to pinch the ball and kick downfield to swing the momentum back in Ireland's favour with Quinn also putting in some crucial tackles.
Ronaldson converted his second penalty kick two minutes later after a period of Scottish indiscipline with Ireland closing out the first half in impressive fashion.
O'Mahony grabbed his second try in the 37th minute after a superb 40-metre run forward, bursting through an initial tackle and sidestepping clear as he helped Ireland stretch ahead on the scoreboard.
Ronaldson added the extras and although Scotland had chances late in the half, poor passing cost them close to the line as Twomey's men turned around with an 11-point advantage.
The visitors upped their game when play resumed, with Ireland under constant pressure during an ten-minute spell after the restart.
Scotland were beginning to string together their passes well, with Millar, Kelbrick, Anderson and Thomson combining in the 46th minute, but Curle was brought down by the excellent O'Mahony five metres out.
Ireland dug in determinedly and eventually switched defence into attack, attacking the short side from a scrum and Ballymena clubman McBurney joining the attack at just the right time to score a 54th minute try.
Scottish captain Crombie, who led by example, broke through in the left corner just five minutes later as the visitors stayed in the hunt.
Millar slotted his second conversion to leave nine points between the sides with exactly 20 minutes left on the clock.
Scotland failed to let up and six-and-a-half minutes later, lock McKay crashed over the line to heap more pressure on the men in green.
Millar once again converted, but a surefooted Ronaldson penalty proved to be the decisive score as it gave Ireland enough of a cushion to beat the Scots for the third successive year.
Referee: Luke Pearce (England)