Three Iranian-Americans arrived in Germany after leaving Tehran on Sunday (local time) in a prisoner swap between the US and Iran.
The exchange followed the lifting of most international sanctions on Iran under a deal US President Barack Obama said cut off Tehran's path to a nuclear bomb.
In a sign of sustained readiness to track Iranian compliance with remaining UN curbs, the US imposed fresh sanctions on 11 companies and individuals for supplying Iran's ballistic missile program.
The Obama administration had delayed the step for more than two weeks during tense negotiations to free five American prisoners, according to people familiar with the matter.
Iran conducted a precision-guided ballistic missile test last October, violating a UN ban.
Speaking after the released Americans had left Iran, Obama said Iran would now not "get its hands on a nuclear bomb" and the planet would be more secure.
"This is a good day because once again we are seeing what's possible through strong American diplomacy," Obama said at the White House.
"These things are a reminder of what we can achieve when we lead with strength and with wisdom."
Iranian President Hassan Rouhani hailed the nuclear deal as a "golden page" in Iran's history and said the agreement could be used as a model to resolve other regional issues.
A Swiss plane took Jason Rezaian, the Washington Post's Tehran bureau chief; Saeed Abedini, a pastor from Idaho; and Amir Hekmati, a former US Marine from Flint, Michigan, as well as some family members, from Tehran to Geneva, Switzerland.
Shortly afterwards, the three left for a US military base in Germany, arriving there later on Sunday, a State Department official said.
One more Iranian-American released under the same swap, Nosratollah Khosravi-Roodsari, was not aboard the aircraft.
A fifth prisoner, American student Matthew Trevithick, was released separately on Saturday, a US official said.
Several Iranian-Americans held in US prisons after being charged or convicted for sanctions violations have also been released, their lawyers told Reuters on Sunday.
Rezaian told two Post senior editors in a phone call on Sunday night that he was doing "a hell of a lot better than I was 48 hours ago".
The newspaper, which released details of the conversation with Rezaian, said he "found escape in the fiction he was allowed to read, and today he was avidly reading whatever he wanted".
Rezaian, 39, was arrested in July 2014 and sentenced in November to a prison term. Iranian prosecutors had accused him of espionage, charges the Post had dismissed as "absurd".
Obama called family members of the released prisoners on Sunday, including Rezaian's brother Ali, and Naghmeh Abedini, the wife of the Idaho pastor.
"I am thankful for our president and all of the hard work by the White House and State Department in making this happen," said Abedini, who has appeared with US Republican presidential candidate Ted Cruz, a US senator and a harsh critic of the Iran nuclear deal.