Pepper spray was used during an argument between several young men in the lobby of a hotel in Europa-Park in Rust (Baden-Württemberg).
The gas cloud passed through the entrance hall and around 20 people were slightly injured, a police spokesman said on Thursday evening.
They suffered from irritated eyes and were being treated by paramedics.
Among the injured were a number of people who had nothing to do with the dispute.
The spokesman said that the reason for the argument in the lobby had yet to be clarified.
Europa-Park is Germany's largest amusement park.