The session in rebel-held Sanaa was the first in almost two years, and comes after the Huthis rejected a UN peace plan and appointed a council to run the country.
Parliamentary sources said 91 lawmakers in the 301-member national assembly attended, and all voted in favour of the council created last week.
The Huthi rebels overran Sanaa in September 2014 and then fought their way into other parts of Yemen, forcing Hadi and his government into exile in Saudi Arabia.
A Saudi-led coalition has been fighting the Huthis and their allies -- supporters of ousted president Ali Abdullah Saleh -- since March last year to shore up the Hadi government.
After Sanaa's capture, many parliamentarians also sought refuge in other towns or overseas.
Political and security sources in Sanaa told AFP that some lawmakers were forced to attend Saturday's session after rebel threats, but without elaborating.
Parliament chief Yehya al-Raie, a leading figure in Saleh's General People's Congress party, urged all MPs "outside the country to review their positions" and invited them to retake their seats.
Hadi denounced the session as a "violation" of the constitution and a "crime punishable by law", in remarks carried by the official sabanew.net website.
"Whatever takes place at this meeting has no legal effects and cannot be implemented," he said.
According to the constitution, more than 150 lawmakers must be present for a vote to be held.
Armed rebels were inside parliament for Saturday's session, held as coalition warplanes pounded military targets around Sanaa, parliamentary sources said.
UN envoy Ismail Ould Cheikh Ahmed has described the rebel governing council as a violation of commitments to the peace process.
Last week, he suspended UN-brokered talks between rebels and the government.
The UN says that more than 6,400 people, mostly civilians, have been killed in Yemen since the coalition air campaign began in March last year.
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- Sanaa airport remains shut -
Arab coalition air strikes have hit rebel positions across northern Yemen as well in as the southwestern province of Taez as ground fighting raged.
Huthi spokesman Mohammed Abdulsalam wrote on Facebook on Saturday that Sanaa airport would remain shut for at least three more days after being closed since Tuesday.
Abdulsalam said the rebel delegation from the Kuwait talks was still stranded in Muscat, where it had made a stopover.
He lashed out at the United Nations which "had promised" to secure his delegation's flight to Sanaa.
"It is not strange for those who have let down Yemen's children to break other promises, forcing us to review the way we deal with (the UN) next time."
The United Nations Humanitarian Coordinator in Yemen, Jamie McGoldrick, said in a statement Friday he was "deeply alarmed by the intensification of violence across the country".
He said the people continue to bear the brunt "as a result of the inability of the parties to find a political solution" to the conflict.
McGoldrick said dwindling foreign currency reserves meant importers found it hard to secure credit, "making it nearly impossible for government entities to maintain basic social services".
"The return to full-scale hostilities only drives humanitarian needs further."
The fighting in Yemen has driven 2.8 million people from their homes and left more than 80 percent of the population needing humanitarian aid, the UN says.
A government statement criticised McGoldrick’s remarks, saying he should have blamed the violence on "the bloody (rebel) coup and their continuing attacks".
"It is stunning that the (UN coordinator's) statement mentions the depletion of foreign currency reserves in the Central Bank without clearly pointing to who was behind this," it added.
The government accuses the rebels of having "robbed" the Central Bank to finance their war, leaving the "public treasury bankrupt".
In Saudi Arabia, the civil defence agency announced that five foreign residents were wounded in shelling from Yemen Saturday in the Jazan border region, without giving their nationalities.
Around 100 members of the Saudi forces and civilians have been killed inside the kingdom's borders since the coalition campaign began.