Christophe Naudin, 55, was released on Saturday so that he could undergo care in hospital and rest, according to his lawyer, Stephen Monod.
He had also become eligible for release for good conduct, the lawyer said.
Naudin had already been hospitalised on being transferred to France in February and suffered from a chronic thyroid problem and a tumour in his head, according to Monod.
He was sentenced to five years in prison in the Dominican Republic in 2016 for helping two French pilots, Bruno Odos and Pascal Fauret, flee the country while they were awaiting appeal against 20-year sentences.
In a case that became known as "Air Cocaine", the pair were detained aboard a private plane they had been hired to fly.
It was found to be carrying 680 kilos of cocaine but they denied knowing of the drugs' presence.
Naudin was part of a group, including French National Front MEP Aymeric Chauprade, who helped them escape to France, where they were later imprisoned.
He was picked up in Egypt in 2016 and extradited to the Dominican Republic to stand trial.
He did not deny his role in the escape attempt, claiming that he was "righting an injustice".
A support committee has been campaigning for his release.