The one-day conference in the capital Baghdad discussed regional security, diplomacy and economic issues, a parliamentary spokesman told media.
Iran, now one of Iraq's closest allies in the region, but a fierce opponent of Saudi Arabia, was represented by a "senior official," the spokesman added.
The conference was hosted by Iraq's youngest-ever speaker of parliament, the 38-year-old Mohammed al-Halbusi, who said Friday that his country was "honored by the presence of its neighbors in Baghdad."
The participating countries pledged to support stability, reconstruction and development in Iraq, which has been ravaged by several decades of conflict, including a three-year battle against the "Islamic State" (IS) militant group.
"The stability of Iraq is necessary for the stability of the region," read the conference's concluding statement.
The participating nations did not announce any diplomatic breakthrough.
Read more: Iraq, Iran to expand cooperation, despite US sanctions
A tough diplomatic jobIraqi Prime Minister Adel Abdul Mahdi recently visited both Iran and Saudi Arabia, which vie for dominance in the Middle East. The two regional foes are at odds across the deeply divided region, with both Riyadh and Tehran supporting different groups in war-torn countries like Yemen and Syria.
Read more: Yemen is 'the biggest humanitarian disaster in the world'
Saudi Arabia, a Sunni-majority country, is a close ally of the US, while Iran, a Shiite country, is one of Washington's "worst enemies" in the region. Earlier this month, US President Donald Trump's administration designated Iran's elite Revolutionary Guard a terrorist organization.
Iraqi PM Mahdi says his country wants to maintain strong relations with Iran, but also with the United States and Saudi Arabia.
Ties between Turkey and Iran have also deteriorated since the start of the Syrian war in 2011. Ankara and Tehran have backed rival groups in the eight-year war that has killed hundreds of thousands of Syrians and displaced millions.
The Baghdad conference was also attended by a large Syrian delegation, led by parliament chief Hammudeh Sabbagh.
As part of its mediation efforts, Iraq is seeking to bring Syria back into the Arab League regional group.
However, Iraq's regional mediation efforts are being lauded as Saudi Arabia and Iran participating in the same events is extremely rare.
shs/rc (AFP, Reuters)
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