A ministerial statement said on Sunday that al-Maliki had called for a complete reshuffle.
The statement said: "The prime minister called for a complete ministerial reshuffle in accordance with the current situation."
Al-Maliki says the changes are to remedy failures to end sectarian violence and reverse the country's economic collapse.
Despite signs of agreement, parliament took a no vote, claiming that al-Maliki gave no details on what changes he might make, chamber officials said.
Al-Maliki, who has been in power for six months, told an Iraqi newspaper on Saturday: "By this reshuffle, we want to send a message to all ministers that they may be replaced if they don't succeed.
Khaled al-Attiya, the Shia deputy speaker, who chaired the closed session, said: "The government's performance has been unconvincing.
"That's why the prime minister wishes to change the cabinet. What we want now is to develop its performance."
"The cabinet was formed to achieve a political consensus. But some ministers have not been competent. So we need change."
Ali al-Dabbagh, a government spokesperson, said there had been a "good response" and said the blocs in parliament, most of which have posts in the coalition, had themselves wanted a reshuffle.
He said he did not expect all ministries to change hands, though the premier's language indicated that the scope of the reshuffle was greater than the handful of posts al-Maliki said he wanted to reassign in August.
Individual ministers could be replaced and there could be changes in the distribution of the ministries among the blocs. The division of ministries followed months of argument after last December's election.
Sunni and Shia acceptance
The spokesman for the main Sunni Arab bloc, the Iraqi Accordance Front, said there was broad agreement that change is needed.
Leading Sunnis have complained that their voice is not being listened to by the Shia-dominated administration.
Saleem al-Jibouri said: "We have yet to discuss the issues but there is a consensus that change is needed.
"Every minister is open to replacement without exception and ministries may even change hands between political blocs as long as the balance is maintained."
Nasser al-Saadi, a member of parliament for the Shia movement of cleric Muqtada al-Sadr, said: "Parliament has given him a free hand to make any reshuffle he wants."