JT will perform in the Phoenix Park this evening to 40,000 screaming fans.
But the Suit & Tie singer touched down in Dublin on Monday night to take in the sights and sounds of the city.
The 32-year-old is rumoured to be staying at the five star Four Seasons hotel in Ballsbridge. And Jessica (31) is supporting her man and making the most of the Irish heatwave.
It will be Justin's first time in Ireland since his performance at the RDS in 2007. The former N*Sync star has tomorrow off so will be hitting some of Dublin's top hotspots.
"When you're constantly gigging, having a day off is a real luxury," a source said.
"He performs in London on Friday and hasn't been in Ireland for a while, so it looks likely he'll hit some Dublin clubs."
He will most likely head to Lillie's Bordello or Justin Bieber's favourite haunt, Everleigh Gardens, after he performs. But ahead of all the body popping on and off stage, it's rumoured that Justin has requested a somewhat bizarre list of backstage demands.
Timberlake has asked concert bosses to provide Hershey's chocolate, pickles and packets of anti-wind tablets in his dressing room.
"When he's travelling and on the road he can get quite bloated which can be quite uncomfortable when you're on stage, so he likes to have some packs backstage just in case," an insider said.
It's not the first time Justin's backstage demands have raised eyebrows.
Later this summer, the Sexy Back singer will hit the road with rapper Jay Z as part of the Legends of the Summer Tour.
The pair have requested a professional cigar roller to accompany them so they can puff on the finest cigars and down neat glasses of whiskey after each performance.
Tonight he will be supported by Jesse J and X Factor winner James Arthur.
Jesse J performed at The Marquee in Cork on Sunday night. "Cork tonight I will never ever forget! You were an incredible crowd and made me feel so amazing," she wrote after the gig.
Tonight's Phoenix Park show will be followed by The Killers on Saturday and Mumford & Sons on Sunday.