Justin Timberlake & Jessica Biel attend the Variety's 4th Annual Power Of Women Event on October 5, 2012. Credit: Jonathan Leibson/WireImage

What did Justin Timberlake wear to his 32nd birthday party? A suit and tie, naturally! The actor-singer turned one year older on Thursday (Jan. 31) -- and marked the occasion the evening before with close pals at Varnish, a speakeasy-style bar in downtown Los Angeles, sources tell Us Weekly.

"It was a dressed-up occasion," one insider tells Us, adding that Timberlake's wife of three months Jessica Biel donned an "amazing vintage Gucci dress that stunned" for the bash. Other guests included Chris Rock, Timbaland and singer Rosette.

Toasting the birthday boy, revelers quaffed Varnish's acclaimed cocktails and champagne. "Everyone partied late," the insider adds. "Justin and Jess looked in love -- he was glad to have his crew around him."

Timberlake certainly has a big year ahead of him: With hit track "Suit and Tie" as its lead single, his new album The 20/20 Experience (his first in seven years) drops next month, with a Grammys performance slated for next Sunday (Feb. 10).

"A lot of music people in the house were talking about his record," a second source notes of the shindig. "He seemed genuinely excited about it and performing."