| Locality | Post Code |
|---|---|
| Apple Grove, Mason | 25502 |
| Arbuckle, Mason | 25123 |
| Ashton, Mason | 25503 |
| Clifton, Mason | 25260 |
| Gallipolis Ferry, Mason | 25515 |
| Glenwood, Mason | 25520 |
| Grimms Landing, Mason | 25123 |
| Hartford City, Mason | 25247 |
| Henderson, Mason | 25106 |
| Lakin, Mason | 25287 |
| Leon, Mason | 25123 |
| Letart, Mason | 25253 |
| Mason, Mason | 25260 |
| Mount Alto, Mason | 25264 |
| New Haven, Mason | 25265 |
| Point Pleasant, Mason | 25550 |
| Robertsburg, Mason | 25123 |
| Southside, Mason | 25187 |
| West Columbia, Mason | 25287 |