The resolution, written by Britain, France and Germany with help from the United States, was adopted unanimously on Friday by the International Atomic Energy Agency's 35-nation board of governors.
Iranian Foreign Minister Kamal Kharazi criticised it but said Iran would meet its commitments to the UN nuclear watchdog.
The resolution called for the IAEA's 15-month-old investigation into Iran's nuclear activities to be stepped up and for Tehran to do more to help it complete the probe within a few months.
The resolution repeats a call by IAEA Director-General Muhammad al-Baradai. He had said: "It is essential for the integrity and credibility of the inspection process to bring these issues to a close within the next few months.
"Iran's cooperation has not been as full, timely and proactive as it should have been."
The resolution was tabled on Thursday at an IAEA board meeting in Vienna, even though the agency admitted it had made a mistake in its investigation.
Iranian President Muhammad Khatami had also warned that the Islamic republic could back away from voluntary commitments such as the suspension of uranium enrichment if the resolution went through.
Resolution, "a major departure from the reality on the ground"
Amir Hossein Zamaninia,
official, foreign ministry, Iran
Iranian Foreign Ministry official Amir Hossein Zamaninia said that the resolution was "a major departure from the reality on the ground," where Iran claims to be cooperating fully.
Washington said it was happy with the resolution. State Department spokesman Richard Boucher on Thursday said: "The United States has felt that it's important for the IAEA to continue its pressure on Iran, to continue its investigation, its inspections, to continue finding things out about this programme."
Boucher also accused Iran of new attempts to hide sensitive activities, particularly razing nuclear sites to hide banned nuclear activity.