In a resolution, MEPs said Saeed Abedini, a naturalised US citizen who converted from Islam to Christianity, should be released "without delay," as should others held for their religious beliefs.
There were concerns that Abedini may have suffered "physical and psychological violence" in prison, it said.
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In August, a Tehran appeals court upheld the eight-year prison sentence against Abedini, ignoring appeals, including from US Secretary of State John Kerry, that he be freed.
MEPs also called for the release of seven members of the Iranian opposition, including six women, who were taken in a September raid on the Camp Ashraf refugee camp northeast of Baghdad.
The resolution, which said the seven were now believed to be held in the Iraqi capital, "calls for their immediate and unconditional release" and condemned the attack on the camp which left 52 people dead, according to the United Nations.
EU foreign affairs head Catherine Ashton warned last month of the risk that the seven could be returned to Iran.