Team Melli beat China (25-22, 25-18, 25-21) in Pool 1 in Jiangmen, China.
Amir Ghafour led Iran with 19 points and Chinese Zhejia Zhang scored 8 points.
Iran, who had defeated Italy 3-1 in its first match, will face Germany on Sunday.
Earlier on the day, Italy defeated Germany 3-0.
The 2019 FIVB Volleyball Men's Nations League is the second edition of the FIVB Volleyball Men's Nations League, an annual international men's volleyball tournament contested by 16 national teams.
The competition will be held between May and July 2019 and the final round will take place in the Credit Union 1 Arena, Chicago, United States.
This is the first edition of the World League or the Nations League to have the Final Round hosted in North America.