“A Tunisian connected to Anis Amri was expelled from Germany on Wednesday,” said prosecution spokesman Sofiene Sliti.
Amri allegedly rammed a truck into a crowded Christmas market in Berlin on December 19, killing 12 people, before being shot dead four days later by police in Italy.
The extradited Tunisian, whose identity was not revealed, “was not involved in the attack in Berlin” but would face charges for “belonging to a terrorist group”, said Sliti.
Tunisian authorities say they have evidence that he aimed to join a jihadist group in Syria.
Shortly after the Berlin attack, authorities in Tunisia arrested four suspects before concluding that they had “no connection” to the attack.
But a nephew of Amri remains in detention in Tunisia, also on suspicion of having intended to join jihadist organisations.