Bold-faced birthday bash! Justin Timberlake and wife Jessica Biel were on hand to help celebrate pal Timbaland's 41st birthday on Thursday, March 14, joining power players Jay-Z, Beyonce, and Chelsea Clinton.

The "Suit & Tie" singer, who wore a large black fedora and dark scarf (no tie!) for the snazzy, casino-themed affair, held at his Hell's Kitchen restaurant Southern Hospitality, arrived at the event around 8:30 p.m. with Biel, 31, by his side.

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The Playing for Keeps actress made a fashion statement of her own, donning a cream-colored silk, collared shirt with a bow tie, black crocheted pants and a black Chanel bag.

The pair mixed and mingled with the star-studded crowd throughout the night, though Timberlake, 32, would often "come over and kiss her and talk to her one-on-one," one eyewitness tells Us.

The crooner spent much of the evening chatting with his "Suit & Tie" collaborator, Jay-Z, the onlooker said. At one point, the musical pair even escaped to the downstairs casino to play blackjack while Biel and a female friend tried their hand at roulette (proceeds from the night went to Timbaland's charity, the Always Believing Foundation).

When Timbaland -- boasting a dapper bow tie -- and wife Monique arrived around 10 p.m., Biel congratulated the host and hostess for the Neuro Drinks-sponsored fete. DJ Ani Quinn provided the music for the low-key bash.

"What a great party! Thanks for having us," the actress said, according to the onlooker.

Beyonce popped by about an hour later, dressed down in wedge sneakers, a bomber jacket and no makeup, coming directly from a rehearsal at the Brooklyn Navy Yard.

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Also on-hand to celebrate the music producer's birthday were Missy Elliott, Jamie Foxx and Chelsea Clinton.

The NBC correspondent and husband Marc Mezvinsky kept with the event's dress code, both clad in suits (Clinton wore a fitted black blazer over a cream-and-orange top) -- and on Mevinsky, yes, a tie.

This article originally appeared on Justin Timberlake, Jessica Biel, Chelsea Clinton, Beyonce Celebrate Timbaland's Birthday: All the Details