| Nominativ | fideicommissus, fideicommissa, fideicommissum | fideicommissi, fideicommissa, fideicommissae |
| Genitiv | fideicommissi, fideicommissi, fideicommissae | fideicommissorum, fideicommissorum, fideicommissarum |
| Dativ | fideicommisso, fideicommisso, fideicommissae | fideicommissis |
| Akkusativ | fideicommissum, fideicommissum, fideicommissam | fideicommissa, fideicommissos, fideicommissas |
| Ablativ | fideicommissa, fideicommisso, fideicommisso | fideicommissis |
| Vokativ | fideicommissa, fideicommissum, fideicommisse | fideicommissi, fideicommissa, fideicommissae |
