Massud Pezeshkian received his certificate of appointment to the post after being elected president of Iran, DPA reported.
He received the official document and blessing from Supreme Leader Ayatollah Ali Khamenei and was then declared the ninth president of the Islamic Republic.
The ceremony in the mosque "Khomeini" in the capital Tehran gathered the political elite and also a number of foreign diplomats.
Pezeshkian is now due to take the oath of office in front of the parliament on Tuesday. He will then introduce the vice presidents and his cabinet ministers.
Pezeshkian, who is considered a moderate, won the presidential election at the beginning of the month after a runoff against hardline candidate Saeed Jalili.
However, regardless of this, in Iran, according to the constitution, the political and religious head of the state is Khamenei, and he has the final say on all strategic issues.
The snap election was called after the death of previous incumbent Ebrahim Raisi in a helicopter crash in May.
Prezeshkian, a 69-year-old heart surgeon and former lawmaker, is considered loyal to the system, but during the election campaign he promised reforms in domestic and foreign policy.
"We have given people a new hope, which we should not turn into a new hopelessness," said the new president.