Raisi's tour, the first in 11 years by an Iranian leader, focused on strengthening global diplomatic ties following years of international isolation.
Mnangagwa urged nations targeted by Western sanctions to band together as he hosted Raisi.
Iran and Zimbabwe are both sanctioned by the United States — Zimbabwe has individuals sanctioned by the U.S. and the European Union over alleged graft and human rights abuses.
"It is critically important that we, the victims of Western sanctions, are talking to each other ... that we show them that we're united," Mnangagwa told a press briefing after talks with Raisi.
The two leaders signed "a record" 12 agreements on topics ranging from energy to telecommunications Mnangagwa said.
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Zimbabwe's President Calls for Unity with Iran
Ashlegh Pfunye, the chief secretary of the Harare-based Citizens Manifesto, a non-governmental policy and governance organization, applauded Mnangagwa's administration for its attempts to strengthen ties with Iran but cautioned the move due to the two countries' shared history of Western sanctions.
"I think our ties shouldn’t be based on that. That is why it is important to understand our interests because we end up finding our ties on levels that don’t build countries," Pfunye told VOA.
Pfunye says Zimbabwe must prioritize internal governance that can impact the removal of sanctions.
Melody Muzenda, a spokeswoman for Zimbabwe's ruling ZANU-PF, differed with Pfunye, arguing Raisi's visit "shows we (Zimbabwe) have good relations with other countries."
Prior to the trip to Zimbabwe, Raisi visited Kenya and Uganda, where he had diplomatic talks with his counterparts William Ruto and Yoweri Museveni.
Nasser Kanani, Iran’s foreign ministry spokesperson said Raisi’s Africa tour was "a new turning point" which could bolster economic and trade ties with the continent.
Tehran and the three African nations share "common political views," Kanani added.
Bekezela Gumbo, a research analyst at the Zimbabwe Democracy Institute, told VOA, the southern African nation "comes a long way with Iran" — and Russia, which has been vying the support of African nations.
"President Emmerson Mnangagwa is trying to scare the Americans by embracing this relationship," Gumbo said.
Africa has emerged as a diplomatic battleground, with Russia and the West trying to court support over Moscow's invasion of Ukraine, which has had a devastating economic impact on the continent, sending food prices soaring.
Western powers have also sought to deepen trade ties with Africa, along with India and China.
Some information from this report was sourced from Agence France-Presse with contributions by VOA reporter Mlondolozi Ndlovu.