Mrs Zaghari-Ratcliffe arrived at RAF Brize Norton in Oxfordshire just after 1am on Thursday morning.
The mother-of-one, whose husband Richard has long campaigned for her release, left Iran with fellow British-Iranian Anoosheh Ashoori, 67, on Wednesday after their release was secured.
Mrs Zaghari-Ratcliffe and Mr Ashoori, who was detained in Evin prison for almost five years, were accused of plotting to overthrow the Iranian government and of spying respectively, which they have consistently and vigorously denied.
They both smiled and chatted as they walked from the aircraft into a reception building at the airport.
Mrs Zaghari-Ratcliffe waved to the cameras, while Mr Ashoori, who was carrying a magazine, gave a salute.
Mr Ashoori appeared to be taking photos with the pilots in the cockpit on the plane, as they waited to disembark.
He could be seen posing with two men through the windows of the cockpit.
Sharing photographs from the flight on Twitter Stephanie Al-Qaq, director for the Middle East and North Africa at the Foreign Office, said there was “relief and joy” as the British-Iranians and officials left Tehran.
A third British detainee, Morad Tahbaz, has been released from prison on furlough but remains in Iran.
Mr Ratcliffe and the couple’s daughter Gabriella, who were waiting at RAF Brize Norton for the Government-chartered flight, were due to enjoy their family reunion in private.
Foreign Secretary Liz Truss is also understood to be at the RAF base.
The release of Mrs Zaghari-Ratcliffe and Mr Ashoori follows months of intensive diplomatic negotiations between London and Tehran, including the eventual payment of an outstanding £400 million debt owed by Britain to the regime.
Mrs Zaghari-Ratcliffe and Mr Ashoori were initially taken to the Gulf state of Oman, which has been closely involved in the behind-the-scenes negotiations to secure their freedom.
Earlier, Prime Minister Boris Johnson thanked the Omani Government for its help in bringing the pair home.
Speaking on a visit to Saudi Arabia, he said: “It is fantastic news that Nazanin is out.
“I am thrilled also for Anoosheh Ashoori and Morad Tahbaz who are also out.
“It has been a lot of work by a lot of people. I want to pay particular tribute to her husband Richard.
“It is fantastic that she will be able to come back, see her family, see her daughter Gabriella.”
Mrs Zaghari-Ratcliffe was detained on security charges by the Iranian Revolutionary Guard at Imam Khomeini airport after a holiday visit to Iran, where she introduced her daughter Gabriella to her parents.
Mr Ashoori was arrested in August 2017 while visiting his elderly mother in Tehran.
In the Commons, with Mr Ratcliffe and Gabriella, seven, watching, Ms Truss set out details of their release.
“It was only when we heard that the wheels were up in Tehran that we really knew it was happening,” she said.
Tulip Siddiq, who is Mr Ratcliffe’s MP, told ITV’s Peston programme about how Mrs Zaghari-Ratcliffe had been able to come home.
She said: “She was contacted by the Islamic Revolutionary Guards in Iran over the weekend and asked to come in for questioning, and quite apprehensive – she messaged me before she went. To her utter surprise, at the end of the questioning, and there were some scare tactics in there, she was given her British passport back.
“Bearing in mind she hasn’t seen her British passport since the 23rd of April 2016. But just as she was about to leave the door, they said to her, ‘don’t book your own flight, we will sort out the flights for you’.
“So after that, I had an idea that she would be coming back, but it’s always touch and go with these things – we’ve had so many false dawns, I didn’t know for sure.
“But the minute she was at the airport, I had a message from Richard Ratcliffe saying Nazanin is at the airport and to her surprise Anoosheh was there as well, who was the other detainee, (a) British citizen. We didn’t think he was coming home, because he wasn’t under house arrest, he was actually in Evin prison.”