Around 30 people began picketing the Amazon warehouse in Bad Hersfeld at midnight, a spokeswoman for union Verdi said, with more expected to arrive at 9 am.
The strike is expected to last all day and possibly into Tuesday.
"As long as Amazon denies employees respect and protection through collective bargaining, we'll keep up the pressure," Verdi board member Stefanie Nutzenberger said.
Verdi has been attempting to bring Amazon to the negotiating table to treat its members at the American online giant as retail workers.
Amazon has repeatedly refused, saying that it is a logistics company.
Around 9,000 people work at Amazon's nine sites across Germany.