Arriving around 11:30 p.m., Lowe wore a black leather jacket over a white shirt, while Giudici opted for a little black dress. Although Lowe's DWTS partner Peta Murgatroyd was also in attendance, the couple didn't spend much time with her.
As the night continued, Lowe and Giudici were "very affectionate with each other," an onlooker tells PEOPLE. "At one point around midnight, Sean rubbed Catherine's neck. Later, Catherine grabbed Sean's face and gave him a peck on the lips."
When the deejay played Whitney Houston's "I Wanna Dance with Somebody," Giudici "got really excited and started dancing" while Lowe watched from a couch.
Even though the pair seemed to be having fun, they called it an early night, leaving around 12:50 a.m.
– Jennifer Garcia