Ok-Seok Seo was traveling with another inspector from the International Atomic Energy Agency near the Khandab nuclear complex in central Markazi province when their vehicle overturned, state news agencies said, citing Iran's Atomic Energy Organization.
The IAEA issued a statement saying it was informed of the accident and has been in touch with the inspectors' families and Iranian authorities.
The other inspector was from Slovenia, the agency said.
IAEA inspectors visit Iran regularly to look at Iran's nuclear sites. Senior teams went to Iran earlier this year in an effort to address concerns raised in an agency report last November that Iran may be conducting research aimed at making bombs.
Iran denies allegations that it is working on nuclear weapons and says its program is solely directed toward developing civilian nuclear energy.