The development comes days before Obama makes a historic visit to Cuba, a milestone in the political rapprochement between the former Cold War foes.
The four dissidents -- Niorvis Rivera, Aracelio Riviaux, Vladimir Morera and Jorge Ramirez -- previously had been released in 2014, only to be subsequently rearrested.
"They were taken out of their jails Tuesday and taken to the Combinado del Este prison in Havana, where they filled out their immigration paperwork and traveled the same day to the United States," Jose Daniel Ferrer, a dissident, told AFP.
Ferrer, who is among a group of dissidents slated to meet the US president Tuesday in Havana, said the release was "like a gift for Obama."
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The Roman Catholic Church had acted as a mediator in the releases, he said.
"This is a gift, a morally very controversial present," said Ferrer, who leads the banned Patriotic Union of Cuba. "The Cuban regime feels that the best thing it has to negotiate with are the political prisoners."
He said Rivera had not wanted to leave Cuba without his family members, but agreed to go after the government promised that they would follow in 10 to 15 days.
The four were jailed again a year later.
Morera, who was on a hunger strike for more than 80 days last year, "is well and happy, although he is still suffering from the after-effects" of the prolonged fast, his son Vladier said.
"He had no idea that he would be freed or about the trip until the last minute, but he's already there," he said. "He's happy, and he told us that the family would reunite over there."