Dolphin ended Cork Constitution's unbeaten run at Musgrave Park when an inspirational try by Darren Sweetnam midway through the second half decided this contest.
Con' came storming back in the closing stages but a gallant Dolphin defence held firm to claim a long overdue league victory over their great rivals.
Con' played with the wind in the opening half but it was Dolphin who had the early chances with Rory Scannell off target with a drop goal effort and a penalty inside the opening minutes.
Johnny Holland put the visitors ahead with a penalty on eleven minutes but Rory Scannell levelled minutes later to leave the sides3-3 at half time.
Dolphin jumped into the lead two minutes into the second half after Con's scrum half Ryan Foley was yellow carded and Rory Scannell converted the resulting penalty.
Harry Fleming looked like he scored a try for Dolphin minutes later but he was adjudged to have put a foot in touch.
Holland levelled on fifty seven minutes but Dolphin regained the lead on sixty four minutes when a beautiful side step by Rory Scannell setup a gap for Sweetnam to run in for a try.
Scannell's conversion attempt hit the upright but he extended Dolphin's advantage with a penalty minutes later.
Con' rallied in the closing stages but their only reward was a Holland penalty five minutes from time after Dolphin's John Quill was yellow carded.
Dolphin: E Mills; D Sweetnam, J Gleeson, C Bohane, H Fleming; R Scannell, E O'Shaughnessy; B Scott, N Scannell, C Condon; D O'Mahony, D O'Shea; J Quill, R Murphy, J Fitzgerald. Replacements: W Foley, P Ryan, M Cronin, S Hansel, C Bannon.
Cork Constitution: D Lyons; Cathal Quinn, L Duffy, N Kenneally, Chris Quinn; J Holland, R Foley; B Cagney, A O'Driscoll, G Sweeney; C O'Flaherty, S O'Connor; J McSweeney, J Ryan, W Ryan. Replacements: M Abbott, R Burke, J Rochford, L Cahill, C Desmond.
Garryowen 8, Young Munster 9
Garryowen are still chasing their first win of the campaign as last season's runners-up had two late chances with penalties to snatch it but they had to be content with a second bonus point at Dooradoyle, as Young Munster won the bragging rights thanks to three penalties by scrum-half Brian Haugh.
Garryowen dominated for long spells and scored the only try of a lively contest in which a player from each side was sent to the bin at different stages of the second half.
Garryowen were quick to gain control but despite their pressure at various stages of the first half they found themselves 6-3 in arrears at the interval.
Jamie Gavin and Brian Haugh exchanged penalties and Haugh had a second for Young Munster but he also missed a few kickable chances.
Midway through the second half Garryowen scored a delightful try. Out half Jamie Gavin floated a superb cross field kick which was gathered by James McInerney who touched down but it was too far out for Gavin to convert.
In a helter skelter last five minutes Garryowen had those two penalty chances but both were missed.
Garryowen: L Bourke; J McInerney, A O'Byrne, A Gaughan, H McNulty; J Gavin, N Cronin; R Brosnan, J Rael, P O'Shea; D Mulcaire, A McCloskey; E Rossiter, A Kavanagh, S Buckley. Young Munster: A O'Loughlin; J McGarry, D Goggin, L Kuntz, D O'Connor; K Hifo, B Haugh; A Cotter, G Slattery, H McGrath; m Madden, S Duggan; A Kennedy, T Goggin, S Rennisson.
Ulster Bank League Division 1A: Clontarf 25, U.C.D. 16;
Dolphin 14, Cork Constitution 9;
Garryowen 8, Young Munster 9;
St. Mary's College 28, Lansdowne 33;
Division 1B: Galway Corinthians 19, Buccaneers 18;