Two commuter trains crashed head-on at high speed near the southern spa town of Bad Aibling on February 9th in one of Germany's deadliest accidents in years, which also left 89 injured.
The dispatcher, whose name has not been released, stands accused of 12 counts of involuntary manslaughter, the prosecutor's office in the nearby town of Traunstein said in a statement.
"There is reason to believe the dispatcher, in violation of a ban, was distracted by using an online computer game directly before the collision of the trains," it said.
The two trains, carrying about 150 passengers in total, were travelling towards each other on a route covered by a single track.
Prosecutors said the dispatcher had mistakenly cleared both drivers to proceed and overrode technical precautions to prevent a collision.
Frantic emergency calls to the drivers did not go through because of a mistake using the radio equipment, "which had the effect that the drivers could not be warned in time".
The trains collided in a forest area about 60 kilometres southeast of Munich, the Bavarian capital.
Authorities said an investigation had ruled out a technical defect as a cause of the disaster.
The accident was Germany's first fatal train crash since April 2012, when three people were killed and 13 injured in a collision between two regional trains in the western city of Offenbach.
The country's deadliest post-war rail accident happened in 1998, when a high-speed ICE train linking Munich and Hamburg derailed in the northern town of Eschede, killing 101 people and injuring 88.
READ MORE: Train crash tragedy rocks southern Bavaria