The Iranians had an impressive start, winning the first set 25-20, however US defeated Iran in the three other sets (25-19, 25-22, 25-21) in Osaka, Japan.
Slobodan Kovac’s men have already lost to Argentina, Poland, Russia, Italy and the US in the competition and have only defeated Tunisia and Venezuela.
The Iranian volleyball players are slated to face Japan on Friday.
The 2015 FIVB Volleyball Men's World Cup started in Japan on September 8, and will finish on September 23.
The tournament is a qualification process for the 2016 Summer Olympics in Rio de Janeiro, Brazil. The top two teams will qualify for the Olympics and join Brazil, which has already secured a berth as the host country.