A 20-year-old man, who was riding the e-scooter along Prestwood Road, was left critically injured and taken to hospital after the collision with a VW Golf at around 3.25pm.
West Midlands Police said he had "serious head injuries", while a 19-year-old woman, believed to have been the e-scooter's passenger was also seriously injured. The woman driving the VW Golf was not hurt.
On Monday, the rider was still fighting for his life after surgery.
Police, paramedics and air ambulance teams descended on the scene near Wolverhampton's New Cross Hospital soon after the collision.
Eyewitness Marcus Burrows said he saw two air ambulances, while photos show air ambulance road vehicles attending the scene alongside West Midlands Ambulance Service and the police.
"Doctors and police came from all over the place," he said.
Prestwood Road was closed for most of Saturday afternoon, with West Midlands Police's serious collision investigation unit tweeting shortly after 9.30pm to say the road had been reopened.
Officers are now carrying out CCTV and house-to-house enquires, and are appealing for anyone who saw what happened, or who has dashcam or other footage, to get in touch via live chat or 101.
Quote log 2690 of 12 June.