Irishman Joshua Molloy has been released by forces in Iraq.
The 24-year-old, who had been fighting against the Islamic State group in Syria, was detained last week for allegedly crossing the Iraqi border.
It was reported that he and two British nationals had entered the country illegally after their visas expired.
Acting Minister for Foreign Affairs Charlie Flanagan welcomed his release and confirmed he is on his way home.
In a statement, Minister Flanagan said, "I would like to thank all those who helped to make this early release happen. My department will continue to provide consular assistance in this case”.