The 20-year-old man was riding the e-scooter along Prestwood Road when he and a woman driving a VW Golf collided at around 3.25pm on Saturday.
West Midlands Police said the man suffered serious head injuries, while a 19-year-old woman, believed to have been the e-scooter's passenger, was also seriously injured.
The 19-year-old woman is still in a serious condition, but appears to be improving, the force said on Tuesday afternoon.
Emergency services sealed off the road near Wolverhampton's New Cross Hospital soon after the collision.
Police, paramedics and air ambulance teams all attended, with witnesses filming the air ambulance helicopter taking off from a nearby field.
The woman driving the VW Golf was not hurt.
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 on the West Midlands Police website or by calling 101.
Quote log number 2690 of June 12.