Flanker Simon Crawford was the star of the show at Anglesea Road as his hat-trick of tries helped move Clontarf into second place in Ulster Bank League Division 1A.
This latest defeat means that Old Belvedere, the 2011 champions, have now gone seven games without a win in the top flight, leaving them in an extremely precarious position as we move into the final weeks of the current season.
Clontarf started the game in bright fashion, and deservedly took the lead seven minutes in when reliable place-kicker Richie Lane comfortably slotted a close range penalty.
'Belvo responded impressively to this early setback and after enjoying some decent spells of possession, they finally opened their account after 22 minutes of play.
Having applied plenty of pressure towards the Clontarf try-line, a long maul on the left flank paid dividends with powerful lock Josh Eden-Whaitiri touching down for the second week running. Winger Josh Glynn added a superb conversion.
After a run of disappointing results, things looked to be improving for 'Belvo, but they found themselves falling behind once more with just five minutes of the first half remaining.
Simon Crawford reached over for his first try of the contest in the left corner at the end of an enterprising move inside the home 22. This was a major boost for the north Dubliners.
With momentum on their side, 'Tarf further increased their advantage on the stroke of half-time when the excellent Crawford broke through the defensive cover for his second try of the night.
Lane was wide of the mark with his conversion attempts on both occasions, but 'Tarf nevertheless would have been pleased to have a 13-7 lead heading into the second half.
Their six-point cushion was cut in half nine minutes after the restart, courtesy of a majestic drop goal from distance by 'Belvo out-half Fergal Lawlor.
With the final half hour of action beckoning, the points were still very much for grabs, but with Crawford crossing the whitewash for a third time with 57 minutes gone, things were starting to look ominous for the hosts.
A 67th minute penalty from Glynn kept 'Belvo in touch, but when centre Killian Lett crashed over to the left of the posts with 11 minutes remaining – securing the bonus point for his side in the process – the game was effectively over.
The rampant north Dubliners were showing no signs of taking their foot off the gas in the closing stages though.
Lett grabbed his second in the 76th minute before winger Michael McGrath completed the rout with his side's sixth and final try.
Referee: Sean Gallagher (IRFU)