Over 2500 representatives from 192 countries took part in the event which focuses on 'Sustainable Development, Citizens, Professions and Territories Relations'.
Ministers are to discuss ways of supporting development by providing access to basic services and financial post services and focus on postal capacities in digital economy, reports IRNA.
The 26th UPU Congress is under will work until October 7.
Delivering a speech in UPU General Assembly on Monday, Vaezi underscored Iran's history and the E-commerce role in the future of post in Iran.
Vaezi is scheduled to meet with some of participating ministers including his Turkish counterpart on the sidelines of the event.
Vaezi met with Chairman of Turkey's Chamber of Commerce and Industry to discuss industrial cooperation and investments between Iranian and Turkish firms.
UPU Congress is held every four years and the 25th edition of the congress was held in Doha, Qatar.
EghtesadOnline: Universal Postal Union Congress opened in Istanbul on Tuesday in the presence of Iran's Minister of Communications and Information Technology Mahmoud Vaezi.