His previous victory was rejected by the incumbent, Laurent Gbagbo, sparking a civil war which killed 3,000 people.
Mr Ouattara’s closest challenger, Pascal Affi N’Guessan, got 9%. He is an ally of Mr Gbagbo who faces trial at the International Criminal Court.
Several candidates withdrew from the poll, saying it was not free and fair.
The 55% turnout was sharply down compared to 80% in 2010.
Mr Ouattara required more than 50% of the vote to avoid a run-off.
The BBC’s Tamasin Ford in Abidjan says that, while the president has been criticized for not doing enough for reconciliation and justice, he has been praised for turning round the economy and returning Ivory Coast to the economic success story it was in the 1970s.