"Secretary Kerry and Foreign Minister Zarif met on the margins of the Munich Security Conference this morning," said State Department spokesperson Jen Psaki.
The face-to-face came ahead of world powers holding their next talks on Tehran's contested nuclear programme February 18.
In an initial accord in November, Iran agreed with the five permanent members of the UN Security Council -- Britain, China, France, Russia and the United States -- plus Germany that it would roll back its nuclear programme and open it to wider inspections.
In return, the world powers agreed to partially lift tough sanctions that have caused immense damage to the Iranian economy.
EU foreign affairs chief Catherine Ashton, who has led the international nuclear talks with Iran, said Friday she had a "really interesting" meeting with Iran's Zarif on the sidelines of the Munich meeting.
Speaking about the upcoming talks to be held in Vienna in just over two weeks, Ashton added: "I very much look forward to working together with you then."
Earlier this month, the United Nations nuclear watchdog, the IAEA, certified that Tehran had stuck to its side of the initial deal, giving access to key nuclear installations and cutting back its enriched uranium stockpile.
Accordingly, the European Union and the United States began lifting some sanctions on January 20, laying the groundwork for the next, six-month stage of the negotiating process.
During this period, the United States and the EU have promised to impose no new sanctions.
The accord provides for ultimately removing the sanctions if Iran lives up to all its commitments.