| Locality | Postal Code |
|---|---|
| Yahata (筑西市) | 309-1112 |
| Yamazaki (筑西市) | 308-0865 |
| Yanagashima (筑西市) | 309-1121 |
| Yanagi (筑西市) | 309-1113 |
| Yanaka (筑西市) | 308-0056 |
| Yawara (筑西市) | 300-4535 |
| Yokoshima (筑西市) | 308-0802 |
| Yokotsuka (筑西市) | 309-1116 |
| Yomogita (筑西市) | 309-1102 |
| Yono (筑西市) | 308-0838 |
| Yoshida (筑西市) | 300-4542 |