He is carrying a message from President Mahmoud Ahmadinejad for King Hamad, state-run media said, amid Bahraini anger at reported comments by a senior Iranian official recalling that the island state had once been under Persian rule.
"Meeting and talking to the Bahraini king and delivering a message from our president tops the agenda for Mr Mahsouli's trip to Bahrain," the state IRNA news agency said.
It said the minister would also take part in a security conference in the Bahraini capital Manama.
The ISNA student news agency said Mahsouli would meet senior Bahraini officials in a bid "to elevate cooperation between the two countries."
Bahrain protested after Ali Akbar Nateq Nouri, a prominent conservative member of Iran's powerful Expediency Council, reportedly said the kingdom used to be Iran's 14th province and had a representative in its parliament.
Iran has since moved to defuse the spat, which has also threatened a major gas deal between the two nations, saying it respects Bahrain's sovereignty.
The relationship between Sunni-ruled Arab states in the Gulf and Shiite Iran has long been strained, with its neighbours wary about the Islamic republic's nuclear drive and its close ties with the new Shiite-led government in Iraq.
The Expediency Council is Iran's top political arbitration body. It has the final say in disputes between parliament and the Guardians Council, a 12-member body dominated by hardliners which is charged with ruling whether legislation conforms with the country's Islamic constitution.
