The UN Office for the Coordination of Humanitarian Affairs said the team comprises representatives from the United Nations Children's Fund, the World Health Organisation and the United Nations Development Programme.
The assessment team is ready to provide any aid that may be needed and to mobilise international assistance, it said.
UN Secretary General Kofi Annan, in a statement, said he was "deeply saddened" by the loss of life and destruction suffered by people of Iran because of yesterday's quake.