At the soiree, guests were dressed in cocktail attire with the men wearing suits and the women donning black dresses. Timberlake, 31, wore a black suit and a fedora; Biel, 30, worked a leopard-print halter dress cinched at the waist with a hot pink belt and matching shoes. Gourmet appetisers were served by Wolfgang Puck Catering along with wine and champagne.
Celebrities on the guest list for the 100-attendee soiree, which included the couple's friends and family: Lance Bass, JC Chasez, Trace Ayala, Ellen DeGeneres, Portia DeRossi and Amy Adams.
"Jessica and Justin were mingling both separately and together throughout the party," an insider tells Us Weekly. "Jessica seems to be very close with Justin's friends and vice versa. You can see that they have been dating for a long time and really know each others friends and family well. The party was a fun celebration and a preview of what's to come with the wedding."
Earlier this month, Biel and Timberlake tried on wedding bands at jewellery boutique Eli Halili in New York City's Soho neighbourhood ahead of making their red carpet debut as an engaged couple at the 2012 Met Ball.
Set to wed this year, the couple of five years spent over a half an hour in the shop with jewellery designer Halili, trying on wedding bands and perusing other pieces in the shop, including one-of-a-kind ancient rings and precious stone necklaces.