|Yes, you can bring pets for free as long as train occupancy does not modify this condition and you comply with the regulations. Dogs must wear muzzles and must be leashed from the moment they enter FGC facilities.
Small animals must travel inside baskets or cages, but they are not allowed to occupy a seat. Dogs considered potentially dangerous according to Law 10/1999, of July 30, cannot be handled by individuals under 16 years old, neither on trains nor at stations (DOGC no. 2948, of 09/08/1999).
According to Decree 170/2002 and Royal Decree 287/2002, the person handling them must have a license and certification of registration in the Municipal Register, the leash must be less than 2 meters, and no more than one dog per person is allowed.