The exhibition which kicked off in the northern province of Semnan and was expected to run until December 26 has been extended to December 29, IRNA wrote.
The organizers extended the event due to the high number of visitors and requests of cultural figures.
The head of the United Nations Information Center (UNIC) in Tehran, Maria Dotsenko, attended the opening ceremony.
Fifty-five historical photos and documents about the presence of prominent Iranian figures at UN events and the visit of seven UN secretary generals to Iran as well as a selection of UN-implemented projects in Iran are publicly available in this exhibition.
Previously, photo exhibitions of UN-Iran cooperation were held in other Iranian provinces including Kerman, Kermanshah, Yazd, Dezful, Bushehr, Zahedan, Shiraz, Sanandaj and Arak.