He was "pardoned" before being freed on "humanitarian grounds", the military government said.
The release was secured after negotiations between the junta and former US ambassador to the UN, Bill Richardson.
Fenster's employer, Frontier Myanmar, said he was on a flight out of Myanmar.
Fenster, who was managing editor of the English-language news site, had been convicted of breaching immigration law, unlawful association and encouraging dissent against the military.
