The one-day summit will bring together parliament heads from Turkey, Saudi Arabia, Jordan, Syria, and Kuwait, a parliamentary spokesman told AFP.
Iran, one of Iraq's closest allies but a fierce foe of Saudi Arabia, will be represented by a "senior official," the spokesman said.
The conference will be hosted by Iraq's youngest-ever speaker of parliament Mohammed al-Halbusi, 38, who said Friday Iraq was "honoured by the presence of its neighbours in Baghdad."
Hours earlier, he had welcomed Syria's parliament chief Hammudeh Sabbagh, who landed in the Iraqi capital on Thursday night with a large delegation.
Iraq has long been at the centre of a struggle for influence between regional and international powers, notably neighbouring Iran and the United States.
But more recently, Baghdad has sought to fashion itself as a mediator among rivals in the Middle East and beyond.
Iraqi premier Adel Abdel Mahdi recently returned from visits to both Riyadh and Tehran, who are at odds across the region and whose officials rarely attend the same events.
Turkey and Iran have also backed opposing sides in Syria's war, which since 2011 has isolated Damascus diplomatically.
As part of its new regional role, Baghdad has sought to bring Syria back into the Arab League.