The singer was among the guests who attended the 50th birthday of MCD supremo Denis Desmond at his Dalkey home.
Bono rubbed shoulders with Pat Kenny and his wife Kathy, Deirdre O'Kane, Slane Castle's Lord Henry Mountcharles and TV presenter Amanda Byram.
Robbie Wooton, U2's manager Paul McGuinness and property tycoon Johnny Ronan were also spotted making their way to the party yesterday.
Others included Michael Colgan, Noelle McCarthy, Jackie Rafter, Graham Beere, Paolo Tuillo, Robbie and Chris Moyles.
And the couple sure know how to throw a party, with two barbecues, a champagne bar, a vodka bar and ice sculptures all laid on for guests.
U2 proved they can still party with the best of them when they stepped out to some of Dublin's top nightspots three days on the trot, following their sell-out Friday and Saturday night gigs.
And they threw a star-studded after-party for family and friends on Saturday night. The famous foursome booked out the entire top floor of a St Stephen's Green club for the bash, with celebs including Bono's artist pal Guggi and singer Sinead O'Connor.
Members of supporting acts on the night, The Kaiser Chiefs and Republic of Loose, were also said to have been in attendance.
One regular at the vastly overrated club, which normally loses VIPs to Krystle, said those who pay the hefty annual membership fee at the club were not allowed upstairs.
Keen to enjoy their celebrations away from the prying eyes of the media, an insider explained how U2 insisted on having a tight security plan to ensure no gate-crashers found their way in.
The Elevation singers are then said to have retired to their city centre hotel, the Clarence.
Tonight will see the boys take to the stage for their final date in Dublin, with The Script and Bell X1 lined up as accompanying acts, and the party of all parties planned for afterwards.
While the details are being kept under tight wraps, it is believed the guys are planning to return to their old haunt, Lillie's Bordello, for the shindig.