Amir Hossein Esfandiar had 18 points for Iran and Hamza Nagga led Tunisia with match-high 19 points at Hiroshima's Green Arena.
Iran national volleyball team will play Argentina on Friday.
The 2019 edition of the FIVB Volleyball Men's World Cup features 12 national teams from the five continental confederations playing in Nagano, Fukuoka and Hiroshima in a round-robin format from October 1 to 15.
The Men's World Cup kicked off for five match days in Fukuoka and Nagano and the teams have moved to Hiroshima for the remaining six match days.