Sayyid Muhammad al-Haydari, Imam of Baghdad's al-Khilani Mosque, told the prayers on Friday that holding joint prayers is a very important step for increasing unity among people and help lessen sectarian conflicts.
Iraq has been experiencing sectarian violence in the past month which the government is being fueled by outsiders.
Joint prayers were held on last Friday for the first time after Iraqi Prime Minister Nouri al-Maliki called for unity among people.
Earlier in May, Maliki warned of attempts to return Iraq to "sectarian civil war".
He called on everyone worried about Iraq's future "to take the initiative, and not be silent about those who want to take the country back to sectarian civil war."
The current violence in the county, he said, “is an intrigue plotted for Iraq, so we call on the politicians to confront this plot by consolidating brotherhood among them and avoid harming their country.”