Jessica Biel isn't just Justin Timberlake's wife -- she's also his biggest fan! After the "Suit & Tie" singer's showstopping performance at the Feb. 10 Grammy Awards, the actress and several other celebs headed over to Hollywood's Palladium theater, where Timberlake continued his hot streak with a sold-out, standing-room-only concert.

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Biel -- who traded her floor-length, one-shouldered Oscar de la Renta Grammys gown for a knee-length red dress -- was "in a great mood and super excited for the show," a source tells Us Weekly. Even before her husband took the stage at 11:30 p.m., she was "bopping around" the exclusive VIP-VIP section with her mother-in-law, Lynn Harless, and a group of women wearing white bow ties. She also happily mingled with Queen Latifah and Michael Bolton.

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(Also in the audience? Former 'N Sync boy bander Lance Bass. However, an insider tells Us that although Bass made it into the VIP section, he wasn't cleared for the VIP-VIP section, where Biel and the rest of Timberlake's pals were.)

The real fun began close to midnight. Still on a high from his successful return to the Grammys stage, Timberlake, 32, wowed the star-studded crowd with a mix of old hits, covers, and new tracks from his upcoming album, The 20/20 experience. He and his 16-piece band jived confidently through a 90-minute set that included "Like I Love You," "Cry Me a River," "Senorita," "Rock Your Body," "Pusher Love Girl," "FutureSex/LoveSound," and the Jacksons' "Shake your Body (Down to the Ground," complete with some old-school choreography.

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Toward the end of the night, the singer welcomed Jay-Z onstage to perform "Suit & Tie." He followed that with "SexyBack," featuring a guest appearance by longtime collaborator Timbaland. At that point, the crowd -- including Biel -- went wild. A source tells Us that the actress was "leaning against the balcony rail and dancing around like crazy to 'SexyBack,' moving her hands all over the place and bopping her head."

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"You can tell she's completely proud of her husband," the onlooker adds of the "beaming" star, 30, who married Timberlake in October. "[She] was clapping like crazy."

This article originally appeared on Jessica Biel Dances "Like Crazy" at Justin Timberlake's Post-Grammys Concert