Officials said Wang was freed as part of a prisoner exchange in which the United States released an Iranian biologist who was nearing the end of his sentence. "Many thanks to all engaged, particularly the Swiss government", he said in a tweet.
Between January 25 and March 10, 2016, Wang visited Iran to attend a Farsi language program at the Dehkhoda Lexicon Institute & International Center for Persian Studies.
"We thank our Swiss partners for their assistance in negotiating Mr Wang's release with Iran".
Both the U.S. and Iranians offered praise to Switzerland who had been acting as intermediaries during negotiations. President Trump later thanked Iran for "a very fair negotiation", and suggested that the swap was proof "we can make a deal together".
While the exchange represents a rare win for both countries, it comes as Iran still faces crushing USA sanctions and the aftermath of nationwide protests that reportedly saw over 200 people killed.
The second US official said Wang would be examined by doctors in Germany, where he was expected to stay for several days.
Wang appeared to be in good health and humour, he said.
"We're hopeful this will lead us to further success with Iran", he told reporters in a conference call.
Soleimani - who works in stem cell research, haematology and regenerative medicine - was arrested by U.S. authorities on charges he had violated trade sanctions by trying to have biological material brought to Iran.
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He was convicted of two counts of espionage in April 2017 and sentenced to ten years imprisonment.
The captive exchange marks a positive step in relations between the USA and Iran, which have deteriorated since Trump pulled the US out of the Obama-era Iran nuclear agreement and increased sanctions against the country.
U.S. Secretary of State Mike Pompeo said in a tweet that he was 'pleased that the Iranian government has been constructive in this matter.' He added 'we will not rest until we bring every American detained in Iran and around the world back home'.
"Our family is complete once again", she said in a statement. Iranian President Hassan Rouhani also said this week that he is willing to sit down and talk, as long as "America is prepared to lift and put aside its wrong, cruel, unlawful, incorrect, terrorist sanctions". It said Soleimani was expected to return to Iran in the coming hours.
Princeton University confirmed the release of Wang.
Hua Qu, Wang's wife, told Reuters she was "happy".
Morad Tahbaz, environmental activist with citizenship from the United States, Iran and Britain, was working with the Persian Wildlife Heritage Foundation doing research on Iran's endangered cheetah population when he and several other environmentalists were arrested a year ago and accused of espionage.
"Wang's wife has got a visa to travel to Germany".
"The highest priority of the United States is the safety and well-being of its citizens", Trump said. "Wang is expected to come to Washington, D.C., on Monday", said Zakka. Iran has responded by gradually removing its commitments under the agreement.
Former FBI agent Robert Levinson, who vanished in Iran in 2007 while on an unauthorized Central Intelligence Agency mission, remains missing as well. US officials, along with human rights groups, said as many as 1,000 Iranians have been killed and thousands more imprisoned since the protests began on November 15.