| Locality | Post Code |
|---|---|
| Okuda (筑西市) | 308-0012 |
| Orimoto (筑西市) | 308-0007 |
| Oshibi (筑西市) | 300-4511 |
| Oshima (筑西市) | 309-1125 |
| Others (筑西市) | 308-0000 |
| Otsu (筑西市) | 308-0041 |
| Otsuka (筑西市) | 308-0813 |
| Oya (筑西市) | 308-0852 |
| Ozakata (筑西市) | 308-0854 |
| Ozeki (筑西市) | 308-0015 |
| Sagishima (筑西市) | 300-4532 |
| Saiwaicho (筑西市) | 308-0848 |
| Sango (筑西市) | 309-1105 |
| Sanodo (筑西市) | 300-4514 |
| Sasazuka (筑西市) | 308-0065 |
| Sekimotoakuto (筑西市) | 308-0124 |
| Sekimotokami (筑西市) | 308-0122 |
| Sekimotokaminaka (筑西市) | 308-0123 |
| Sekimotonaka (筑西市) | 308-0126 |
| Sekimotoshimo (筑西市) | 308-0127 |
| Sekimotowakenaka (筑西市) | 308-0125 |
| Sekitate (筑西市) | 308-0113 |
| Shibayama (筑西市) | 308-0072 |
| Shima (筑西市) | 308-0823 |
| Shimizu (筑西市) | 309-1126 |
| Shimoezure (筑西市) | 308-0851 |