| Singular | Plural | |
|---|---|---|
| Nominativ | fideicommissom, fideicommissum | fideicommissa |
| Genitiv | fideicommissi | fideicommissum, fideicommissorum |
| Dativ | fideicommisso | fideicommissis |
| Akkusativ | fideicommissum | fideicommissa |
| Ablativ | fideicommisso | fideicommissis |
| Vokativ | fideicommissum | fideicommissa |