Dimitris Koufodinas, a prominent member of leftist terror group November 17, was granted his fifth furlough by a prison council on Thursday.
His jail leave starts on Friday and will last for six days.
According to Greek law, prison councils do not base their decision on the type of crime committed or the length of the sentence. Instead, convicts are required to have completed a specific number of years behind bars and must not have received any disciplinary action.
The council also judges whether the convict makes good use of his leave and returns promptly to jail when it expires.
Koufodinas is serving 11 life sentences for multiple murders. November 17 killed 23 people over a period of almost three decades, including politicians, businessmen, industrialists, publishers, as well as American, Turkish and British diplomats and officials.
In August, Koufodinas was transferred from the high-security prison of Korydallos in Athens to a so-called agricultural jail near the city of Volos, central Greece, where prisoners have less restrictions, prompting protests from Washington and Ankara.