Conceptia Ouinsou, the constitutional court's president, said the authorities had uncovered several irregularities, including attempts to stuff ballot boxes, underage voting and pressuring of voters.
However, Ouninsou said: "These irregularities do not damage the credibility of the election."
Speaking late on Saturday, she said that the provisional results would still need to be confirmed by the appeal court if there were a legal challenge.
The ADD is dominated by established forces in Benin politics such as Mathieu Kerekou.
Kerekou, a former president, stood down before last year's presidential election after ruling for most of the previous 30 years.
Yayi, a former head of the West African development bank, won that election on a promise of a new start for Benin and its economy.
The country is struggling as a result of low prices for its main export, cotton, and there is widespread corruption.
But Yayi's campaign to root out fraud has met resistance from vested interests.
When armed men opened fire on his convoy last month, he accused those targeted by his anti-corruption efforts of trying to assassinate him.
After seizing power, Kerekou transformed the former French colony into a Marxist state before introducing what has been in recent years one of the more stable multi-party democracies in West Africa.
Nevertheless, successive elections have been marred by disorganisation and allegations of fraud.
Last month's vote was postponed by six days because bickering within the electoral commission meant that ballot papers were not printed in time.