| Locality | Post Code |
|---|---|
| Burkettsville, Mercer | 45310 |
| Carthagena, Mercer | 45822 |
| Celina, Mercer | 45822 |
| Chickasaw, Mercer | 45826 |
| Coldwater, Mercer | 45828 |
| Fort Recovery, Mercer | 45846 |
| Maria Stein, Mercer | 45860 |
| Mendon, Mercer | 45862 |
| Montezuma, Mercer | 45866 |
| Rockford, Mercer | 45882 |
| Saint Henry, Mercer | 45883 |