The official didn't say when the group, which included Rezaian, former Marine Amir Hekmati, Saeed Abedini and Nosratollah Khosravi-Roodsari, were released.
State Department official Brett McGurk tweeted an image of Rezaian, announcing that the journalist landed safely in Geneva.
Rezaian's brother Ali said in an earlier statement, "I am incredibly relieved that Jason is on his way home.
"Today is an incredible day for all of us," he said.
Around 12:30 p.m. ET today, Abedini's wife Naghmeh posted to Twitter that "Saeed just landed in Geneva."
"He is getting ready to leave to Germany. I should talk with Saeed in just a few hours! Thank you for your prayers!" she wrote.
Hekmati's family said in a statement today, "We have now been officially told that he is on a plane leaving the country.
"It is hard to put into words what our family feels right now," the statement said. "But we remain in hopeful anticipation until Amir is in our arms."
Regarding the next destination for Khosravi-Roodsari, a senior White House official said, "It's his free determination where he wants to go. We don't make that judgment for him."
A fifth detained American, Matthew Trevithick, left the country on a civilian plane Saturday, a senior White House official said.
A senior White House official said the prisoner swap discussions "were very intense."
"Most of them were held in Switzerland, who were instrumental in hosting these talks and allowing them to remain secret," the official said.