The 37-year-old charity worker was arrested at Imam Khomeini airport on April 3 and has since been accused of plotting to topple the Iranian regime.
She was held as she was trying to return to Britain after a holiday visiting family with her daughter Gabriella.
Prime Minister Theresa May last month made a personal appeal to the Iranian president to resolve the case in a telephone call, while an appeal for her release has been signed by more than 800,000 people.
The couple's young daughter who celebrated her second birthday in June without her mother or father, is being cared for by her grandparents in Tehran.
According to her husband Ms Zaghari-Ratcliffe has suffered dangerous weight loss, lost some of her hair and has become virtually unable to wallk.
Amnesty International, which has campaigned for Ms Zaghari-Ratcliffe to be freed, said the case was a "complete travesty of justice".
Its Individuals at Risk campaign manager Kathy Voss said: "This is extremely depressing but probably not unexpected news.
"Iran's Revolutionary Courts are notorious for handing down prison sentences after grossly unfair trials.
"From all the reports we've seen, Nazanin's case has been a complete travesty of justice throughout - beginning with her protracted secret detention, then the unsupported accusations from officials, and culminating in this week's out-of-the-blue sentence."
The mother from Hampstead in London is expected to serve the sentence in Evin Prison.
Ms Zaghari-Ratcliffe told her husband on the phone that she preferred to stay asleep dreaming rather than "wake up each morning and remember where I am".
She said she missed her daughter, asking: "Do you understand what it is like to be a mother kept away from her child this long? I have missed over a fifth of her life."
The mother added that she was "sick" of being used in negotiations, and that the stress of the past five months had made her parents' hair turn white.
Mr Ratcliffe has previously said he believes his wife and child are being used as a "political bargaining chip" and branded the suggestion that she may have been involved in a plot to overthrow the Iranian regime "nonsense".
Monique Villa, the CEO of the Thomson Reuters Foundation, where Ms Zaghari-Ratcliffe is a project manager, said she was "convinced" of her innocence.
She said she was "outraged" at the sentence, which she called "a very serious condemnation that comes without any charges or evidence being made public".
Ms Villa said: "I want to reiterate my total support to Nazanin and her family in these terrible circumstances and I ask the Iranian authorities to release her as soon as possible.
"I am convinced of her innocence and reiterate that she had no dealings with Iran whatsoever in her professional capacity at the Thomson Reuters Foundation."
The foundation will continue to work with Mr Ratcliffe, the UK Foreign Office and the British authorities to find a resolution to this "terrible situation", she said.
From The Express: