This victory in Volleyball World Cup in Japan gave Iran a 2-1 mark in the tournament, while European champion Serbia slumped to 0-3.
Mehdi Bazargarde (17 points) and Mohammad Mousavi (14 points) led a balanced scoring attack for Iran.
Iran played a fine all-around game under the direction of head coach Julio Velasco.
Ivan Miljkovic was the focal point for Serbia, scoring a match-high 22 points.
Dragan Stankovic and Marko Podrascanin added 14 each.