Iran’s Milad Ebadipour scored eight points, while Yuji Nishida collected 15 points for the Japanese team.
Japan clinched the title for the 10th time. Both South Korea and Iran have won the trophy on four occasions.
Iran’s national squad had defeated Hong Kong (3-0), Iraq (3-1), Pakistan (3-0) and China (3-0) to book a place in the final match.
Earlier in the day, Qatar defeated China 3-0 to win the bronze medal.
The Championship was held at the Al-Ghadir Hall in Orumiyeh, Iran from August 19 to 26.
In the latest FIVB rankings, Japan boasts the prestigious title of the highest-ranked Asian team, clinching the fifth spot. Meanwhile, Iran secured the 10th position.