Lopez attended an after party at Chateau Marmont hosted by the owners of DSquared.
The American Idol judge, whose Kohls campaign (#getjenniferthere) and knockout performance made her the No. 1 trending topic on Twitter, wore a black DSquared dress designed by the fashion house's twin brothers, Dean and Dan.
While DJ Big Syphe spun tunes, Lopez, 44, spent the night dancing with boyfriend Beau "Casper" Smart and stunning BFF Leah Remini, with whom she shared a bowl of spaghetti and meatballs.
Robert Pattinson arrived at the party around midnight, wearing jeans, a black leather jacket and black beanie, and hung with friends on the terrace under a heat lamp smoking cigarettes.
Other celebrities at the party included music producer L.A. Reid, singer Akon as well as Dancing With the Stars' Maksim Chmerkovskiy, who performed with Lopez at the AMAs.
Getty Images / Donato Sardella