Mohammadseifi defeated Shi Zhanwei from China 2-0 in the -70kg weight category and won the title.
Iranian athletes had already won eight gold medals in the Games.
Saeid Rajabi in +80kg and Mirhashem Hosseini in 63kg had won two gold medals in taekwondo.
Hassan Yazdani (86kg), Alireza Karimi (97kg) and Parviz Hadi (125kg) snatched three gold medals in wrestling freestyle.
Iranian Greco-Roman wrestlers Mohammad Ali Geraei in 77kg and Hossein Nouri in 87kg had also seized two gold medals.
wushu practitioner Erfan Ahangarian won a gold medal in -60kg as well.
The 2018 Asian Games, officially known as the 18th Asian Games and also known as Jakarta Palembang 2018, is a pan-Asian multi-sport event scheduled to be held from 18 August to 2 September in the Indonesian cities of Jakarta and Palembang.
The athletes compete in 465 events across 40 sports and 67 disciplines.