A series that started in 2014 reached 11 victories in a row for the world champion who still has a work to do to win the group in Varna.
Michal Kubiak was top scorer for Poland with 12 points. Nowakowski, Kurek and Szalpuk each added 10.
For Iran Amir Amir Ghafour recorded a personal high at the championship with 17.
Poland needs a point from its last match against Bulgaria to top Pool D and stays in Varna for Round 2. With the loss Iran was eliminated from contention for the top sport and will play in Pool G in Round 2.
The 2018 championship is the 19th staging of the FIVB Volleyball Men's World Championship, contested by the senior men's national teams of the members of the Fédération Internationale de Volleyball (FIVB), the sport's global governing body.
The final tournament is being held in Italy and Bulgaria from September 9 to 30. For the first time the tournament is jointly-hosted by more than one country.
The final six will be hosted by Italy at the Pala Alpitour in Turin.