The Voice UK coach pulled up to a launch event for his new solo album at The Avalon Club in Beverly Hills in his modified DeLorean, later tweeting a photo of himself and Nicole Scherzinger posing alongside it.
However, five hours later will.i.am returned to the social networking site to report that the vehicle had been taken during the event.
"My car was stolen...what the f**k," he wrote. "Where is my f**king car...??? This isn't funny anymore."
He then tweeted: "I'm going to be optimistic and pray that my car is returned and safe," before adding: "#givemebackmycar this joke is getting old..."
The DeLorean got will.i.am in trouble in June when he was pulled over by police during a test drive.
It was recently revealed that will.i.am and Scherzinger have been working together on the former Pussycat Doll's second studio album.