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