The vote came after a fierce debate among lawmakers over the terms of the accord. The deal will lift nuclear-related sanctions on Iran in return for curbs on its atomic activities.
The debate was not broadcast on television, but Iranian newspapers are reporting angry scenes including some MPs shouting their concerns were not addressed.
A motion to approve the nuclear deal was however passed with 161 votes in favour, 59 against and 13 abstentions, Iran's official IRNA news agency and other media said.
A notorious critic of the nuclear diplomacy, Hamid Rasaie, was pictured on social media holding up a piece of paper declaring: "This is an official violation of law. Parliament is a sham."
“We saw this summer, and in September, a very tough review process of the deal in the US debate,” says Ellie Geranmayeh, a fellow with the European Council on Foreign relations. “It’s a very similar situation in Iran, where there are many different factions some that are opposing the deal, and seeing it as essentially a bad deal for Iran, because it undermines its nuclear program. They see that as a sovereignty issue.”
Iran's President Hassan Rouhani and other officials have faced attacks over the way they engaged with the US and other countries to secure the agreement.
“We saw the Iranian delegation coming back from New York last weekend, following a series of meetings on the implementation of the deal,” explains Geranmayeh. “This again invoked a sense in Iran among the hardliners, that the deal is not just a nuclear deal, but about a bigger opening between the US and Iran.”
Things should start moving quite quickly - Iranian officials have said sanctions should be gradually lifted by the end of the year or January 2016 at the latest.
The deal, which will lift nuclear-related sanctions on Iran in return for curbs on its atomic activities - the Islamic republic denies seeking a bomb -- has been widely hailed as a diplomatic triumph that averts military confrontation and another possible war in the Middle East.
“This sort of nuclear agreement is unprecedented, in terms of the level of detailed implementation on both sides,” says Geranmayeh. “Iran needs to implement very technical, very difficult measures to essentially reshape its nuclear program. How smoothly this program goes remains unknown, there will obviously be bumps on the road.”
There have been concerns, especially in the US, that Iran couldn't be trusted and that it could fail to implement the deal. But Geranmayeh says that this doesn't seem likely now that Iran's parliament and the US Senate have adopted the deal.
There will be inspections of military and nuclear sites by western powers, even though some have criticised the limited access the experts will get to the sites.
But let's not forget that the authorities need this deal too : the country's economy has been badly hit by the sanctions put in place by the US and the EU in 2007. The country is rich in oil and natural gas - and companies in Europe are getting ready to sign new contracts with Iran.
“Iran is a huge market, at least the second biggest in the Middle East with Egypt,” says Thierry Coville, a Researcher at the French research centre for international and strategic studies. “It’s quite a rich country, because Iran has a lot of oil and natural gas it can export. Officially the sanctions will be lifted at the beginning of 2016. For foreign investors it will be possible to be present in Iran next year, but there are a lot of constraints against foreign investment in the country. It can only happen gradually.”