Abadi on Sunday proposed a series of measures to combat corruption, streamline the government and improve services after weeks of protests and a call from Iraq's top Shiite cleric Grand Ayatollah Ali al-Sistani for drastic change.
"It was unanimously approved," parliament speaker Salim al-Juburi announced to applause after the vote, which was held without a debate as soon as the plan was read.
Of 328 members of parliament, 297 attended the session, Juburi said.
But he said that a complementary plan containing even more reforms was needed, and that Abadi should sack ministers who are guilty of negligence and corruption.
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The second plan was also read and approved by parliament, and the session -- most of which was taken up by the reading of the two plans -- ended some 30 minutes after it began.
The approval is a victory for Abadi, but the question now becomes how thoroughly the measures will be implemented, and what politicians and other officials may do to try to thwart them.
"They have to say that they support reform, but they will work against it."
Amid a major heatwave that has seen temperatures top 50 degrees Celsius, protesters have railed against the poor quality of services, especially power outages that leave just a few hours of government-supplied electricity per day.
Thousands of people have turned out in Baghdad and various cities in the Shiite south to vent their anger at the authorities, putting pressure on them to make changes.