He called on Zimbabweans to end violence and support his old rival in rebuilding the country.
"That's what [Susan] Tsvangirai would have wanted, for us to co-exist peacefully," he said.
"We have just started a new life after years of fighting each other and insulting each other. We have said let's give peace and harmony a chance and work together."
'Peace and harmony'
Mugabe and Tsvangirai entered into a unity government in February after disputed elections in early 2008 had led to an outbreak of violence and almost a year of political deadlock.
That government is now faced with the task of tackling a financial crisis that has led to food shortages and the world's highest inflation rate, as well as a cholera epidemic partially blamed on the collapse of the country's health and sanitation systems.
The past political tensions had prompted speculation that Friday's car crash may have been an assassination attempt, but speaking on Monday, Tsvangirai said "if there was any foul play, it was one in a thousand".
"It was an accident and unfortunately it took her [Susan's] life," he said.
A burial ceremony for Susan Tsvangirai is planned on Wednesday in her hometown of Buhera - where she and her husband had been headed on the day of the accident.