The 31-year-old was arrested in Berlin's Kreuzberg district late on Thursday night as he waited at a traffic light in his car. He did not resist arrest, police investigators and public prosecutors said.
The arrest means a total of six suspects have been picked up in the investigation of the robbery, which took place during the European Poker Tour Tournament on March 6 at Berlin's luxury Park Hyatt hotel.
Armed with machetes, the masked men burst into the hotel at Potsdamer Platz at 2:15 pm, overrunning security guards and causing panic among the roughly 400 contestants.
A security guard managed to disarm one of the men, grab a bag full of money and hold the man in a headlock, but he was freed by his accomplices. Several people were injured during the heist, but none seriously.
The men then fled without their masks. They were filmed leaving and also left behind fingerprints and DNA evidence at the scene.