Ali Larijani replaces Ali Akbar Ahmadian, who is due to take on an unspecified new role in the administration of President Masoud Pezeshkian, Tasnim added.
Larijani previously served three terms as speaker of parliament, secretary of the Supreme National Security Council, head of the Islamic Republic of Iran Broadcasting (IRIB), Minister of Culture and Islamic Guidance and advisor to the Supreme Leader.
His appointment may signal a doubling down on Tehran's traditional confrontational stance with Israel and the United States after a punishing 12-day war with Israel in June capped off by US airstrikes on Iranian nuclear sites.
Still, Larijani registered three time to run for president in Iran but was disqualified on two occasions by Iran's hardliner-dominated Guardian Council. His political stances on diplomacy and domestic affairs appear to have softened in recent years.
Larijani ran as a candidate in the ninth presidential election of Iran, held in 2005. He lost the race, finishing sixth out of seven candidates.
The appointment comes with some institutional changes following a 12-day war with Israel in June.
Iran’s Supreme National Security Council (SNSC) is due to form a Defense Council to coordinate military planning and strengthen the armed forces, Iranian media reported on Sunday.
President Pezeshkian will chair the council, which will include the heads of the executive, legislative and judiciary branches, as well as top military commanders and key cabinet ministers, the report added.