RFE/RL contributor Mykola Semena, who has been convicted of separatism in the Russian-controlled Crimea region, moved to mainland Ukraine on February 18.
Semena, 69, is expected to arrive in the Ukrainian capital, Kyiv, on February 19 to receive medical care that he needs to treat a heart condition and damaged spine, RFE/RL said.
The journalist said he was planning to stay in mainland Ukraine "indefinitely," adding: "As long as part of Ukraine is occupied, I cannot consider it my home. My family thinks the same."
RFE/RL President Jamie Fly said the news of Semena's "safety and security is long-awaited and joyous."
"His arrest, almost four years ago, for publishing criticism of Russia's annexation of Crimea, was always wrong and violated every basic human right and freedom," Fly added. "I'm glad Mykola is free and able to resume his writing career for the benefit of the people of Ukraine."
Semena, who has contributed to RFE/RL's Krym.Realii (Crimea Realities) reporting project, was arrested by Crimea's Russia-imposed authorities in 2016 and charged with acting against the "territorial integrity of the Russian Federation."
In 2017, a court handed him a 2 1/2-year suspended sentence and banned him from "public activity" for three years.
But a court in Crimea's capital, Simferopol, last month ruled to prematurely terminate the probation period and expunge his criminal record.
Semena says the accusation against him was politically motivated.
The United States, the European Union, and international media watchdogs have all condemned the trial and verdict.