Police said the suspect's lawyer called investigators prior to the 20-year-old's arrival. Authorities would not confirm the suspect's location prior to departure.
“We are confident that the fourth suspect will also be arrested soon,” police spokesman Frank Millert said.
The 20-year-old Mustafa U. is the third of four suspects now in police custody. On Monday, a 21-year-old German turned himself in to police and provided the names of his accomplices.
He told police he would return his share of the €242,000, which stolen after the armed robbers raided Germany's biggest poker tournament at Berlin's Grand Hyatt hotel.
Two days later, a second suspect was arrested without resistance during a routine security check.
According to a report published Saturday in daily newspaper Bild, the fourth fugitive robber is reportedly in Lebanon and has been in contact with Berlin police.