The crash happened in the northbound carriageway in between junctions 10 and 10a, near Walsall and Wolverhampton, at around 4pm on Wednesday.
Paramedics, police, firefighters and highways officers were all sent to the crash but nobody was seriously hurt.
West Midlands Ambulance Service said four patients were treated for minor injuries and discharged at the scene.
The car that rolled over was the only vehicle involved in the incident.
All but one of the four lanes of the motorway were initially shut northbound as the crash was dealt with before the closure was reduced to one lane at around 5pm.
However delays continued into Wednesday evening, with congestion also reported on the M5 northbound.
Highways England warned drivers to expect delays of at least 40 minutes as a result of the crash, with motorists reporting queues all the way back to Junction 6 Spaghetti Junction in Birmingham.
One driver who passed the crash in the southbound carriageway said: "The overturned car was in the hard shoulder when I went passed at 5pm and there were people walking nearby, but I don't know if there were others more seriously injured.
"Cars were moving really slowly northbound for about 10 miles."
A West Midlands Ambulance Service spokesman said: "We were called at 3:56pm to reports of a single vehicle rollover at junction 11 of the M6 North.
"We sent one ambulance and a paramedic officer and treated four patients for minor injuries and they’ve been discharged at the scene.”