The team of eight European lawmakers will also meet parliament speaker Ali Larijani and the head of the national security and foreign policy committee Alaeddin Boroujerdi during their six-day visit, IRNA said.
The delegation has been tasked with rebuilding links with politicians and broaching human rights issues, a member of the group told AFP before the visit.
Talks with the officials are due to start tomorrow, state broadcaster IRIB said, but the delegation met rights lawyer Nasrin Sotoudeh today.
Belgian MEP Isabelle Durant had said before the visit that delegates would also meet regime opponents and rights activists, including Sotoudeh and filmmaker Jafar Panahi, who both won a European Parliament prize for human rights in 2012.
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According to one participant, the meeting focused on the situation of political prisoners and human rights in Iran as well as lifting the house arrest on opposition leaders Mir Hossein Mousavi and Mehdi Karroubi, and Mousavi's wife Zahra Rahnavard.
Government spokesman Mohammad Baqer Nobakht said earlier that "lifting the house arrests" was on "the president's agenda".
The delegation is composed of leftwing politicians from Finland, Austria, Germany and the Netherlands. Last October, three socialist MEPs visited Iran but their trip was not endorsed by the parliament.
In October 2012, the European Parliament cancelled a planned trip to Iran after authorities refused to allow delegates to meet Panahi and Sotoudeh.
Fars news agency reported that a separate French parliamentary delegation was to arrive in Tehran tomorrow.