Mollaei defeated Sotaro Fujiwara of Japan in the final match in 80 seconds.
It was Iran’s first gold medal in World Championships in fifteen years.
German judoka Alexander Wieczerzak and Vedat Albayrak of Turke jointly won the bronze medal.
On Saturday, Mohammad Mohammadi had won a bronze medal in the -73kg category.
About 800 judokas from 125 nations are competing at the 2018 World Judo Championships which will close on September 27 in Baku, the Azerbaijan Republic.