| Locality | Postal Code |
|---|---|
| Postal/ZIP Codes in Washinosu (茂原市) | 297-0051 |
| Postal/ZIP Codes in Yachiyo (茂原市) | 297-0024 |
| Postal/ZIP Codes in Yagyu (茂原市) | 297-0045 |
| Postal/ZIP Codes in Yamasaki (茂原市) | 297-0061 |
| Postal/ZIP Codes in Yamoto (茂原市) | 297-0011 |
| Postal/ZIP Codes in Yawatabara (茂原市) | 297-0054 |
| Postal/ZIP Codes in Yoshiikami (茂原市) | 299-4122 |
| Postal/ZIP Codes in Yoshiishimo (茂原市) | 299-4121 |
| Postal/ZIP Codes in Yumiwatashi (茂原市) | 299-4105 |
| Postal/ZIP Codes in Niiharukogyodanchi (茂原市) | 299-4129 |