These are the rules for bringing pets on Deutsche Bahn trains: 

• Small Pets: pets up to the size of a domestic cat travel for free. They must be transported in a carrier that fits below the seat or on the shelf above.
• Large Pets: larger pets can travel on trains with a special pet fare, but they must be on a leash and wear a muzzle. In this case, please contact us through the contact form.
• Guide dogs: these dogs travel for free and do not need to wear a muzzle.