Susan Tsvangirai died shortly after the crash which happened on a notoriously dangerous stretch of road outside Harare on Friday.
Tsvangirai apparently told officials that a truck with a trailer was headed towards his vehicle but the driver managed to avoid a head-on collision.
"He is stable. The doctors and the family will make an announcement in due course," MDC Secretary-General and Finance Minister Tendai Biti told reporters outside the hospital treating Tsvangirai.
The crash occurred some 50 km (30 miles) south of Harare as Tsvangirai headed to his rural home in Buhera along the potholed Harare-Masvingo highway, one of the many routes neglected in the economic crisis.
State television quoted police spokesman Wayne Bvudzijena as saying:
"A haulage truck encroached into the lane of the Prime Minister’s car, resulting in a side-swipe which resulted in the Prime Minister’s car, a 4-by-4 Toyota Landcruiser, rolling over three times."
Bvudzijena said Tsvangirai was travelling in an MDC vehicle driven by a private, not government, driver.
Tsvangirai, who turns 57 on Tuesday, had six children with Susan, who was very popular among MDC supporters, who would chant "mother, mother" each time she appeared at rallies with her husband.
Susan, 50, avoided the spotlight but stood by Tsvangirai throughout his ordeals as Mugabe’s most determined opponent. Tsvangirai has faced a treason trial and been beaten in police custody.
It was believed the trailer of the vehicle hit the car Tsvangirai was travelling in, causing it to overturn several times.
Eddie Cross said the prime minister’s car was in the middle of two security vehicles.
"Morgan didn’t have a travelcade. He actually refuses to travel in a travelcade but he had a security vehicle in front and a security vehicle behind so he wasn’t alone. This vehicle simply hit his vehicle, it didn’t hit any of the others," he said.
It was reported that he had swelling on his head but doctors have yet to comment on his condition.
It was also reported that Zimbabwean President Robert Mugabe visited Tsvangirai in hospital.
Cross said officials waited two hours before they could tell Tsvangirai about his wife’s death.
"Clearly he was sedated after the accident. I think he’ll spend the night sleeping. He’s an amazing individual, I mean for a man who’s been under so much pressure, he’ll survive this but he’ll miss her for the rest of his life," he explained.
He said her role in the party was priceless, adding that she would be sorely missed.