The man died on Monday at the plant in Baunatal, about 100km (62 miles) north of Frankfurt, VW spokesman Heiko Hillwig said.
The 22-year-old was part of a team that was setting up the stationary robot when it grabbed and crushed him against a metal plate, Hillwig said.
He said initial conclusions indicate that human error was to blame, rather than a problem with the robot, which can be programmed to perform various tasks in the assembly process.
He said it normally operates within a confined area at the plant, grabbing auto parts and manipulating them.
Another contractor was present when the incident occurred, but was not harmed, Hillwig said. He declined to give any more details about the case, citing an ongoing investigation.
German news agency DPA reported that prosecutors were considering whether to bring charges, and if so, against whom.
