But not in the good way.
Despite having chatted politely during the Golden Globe Awards ceremony earlier this week, the former couple had a run-in later in the night.
According to witnesses, Timberlake was then talking to hottie Jessica Biel when Diaz approached. Jess stepped away - to give them space and fantasize about Derek Jeter, we imagine - as the former flames had a serious exchange.
Diaz walked away, Timberlake followed, and the two were soon spotted engaged in an intense 40-minute face-off in a side room.
Reportedly, JT slammed his fist down after the argument was over. We're not sure why Diaz would be mad Justin was talking to Biel. After all, Scarlett Johansson is the one he's bringing sexy back with.