| Singular | Plural | |
|---|---|---|
| Nominativ | triumuir | triumuirique, triumuiri |
| Genitiv | triumuiri, triumuirique | triumuirum, triumvirorum |
| Dativ | triumviro | triumuiris |
| Akkusativ | triumvirom, triumuirum | triumuiros |
| Ablativ | triumviro | triumuiris |
| Vokativ | triumuir | triumuirique, triumuiri |