| Locality | Postal Code |
|---|---|
| Postal/ZIP Codes in Kotohira (長岡市) | 940-0038 |
| Postal/ZIP Codes in Kotsunagi (長岡市) | 940-0211 |
| Postal/ZIP Codes in Koya (長岡市) | 954-0161 |
| Postal/ZIP Codes in Koyo (長岡市) | 940-2015 |
| Postal/ZIP Codes in Kozawamachi (長岡市) | 940-2102 |
| Postal/ZIP Codes in Kozonemachi (長岡市) | 940-0883 |
| Postal/ZIP Codes in Kukawa (長岡市) | 940-0121 |
| Postal/ZIP Codes in Kumanofukuro (長岡市) | 940-0113 |
| Postal/ZIP Codes in Kumoidemachi (長岡市) | 940-2046 |
| Postal/ZIP Codes in Kuriyamazawa (長岡市) | 940-0155 |
| Postal/ZIP Codes in Kurosaka (長岡市) | 949-4502 |
| Postal/ZIP Codes in Kurozumachi (長岡市) | 940-0007 |
| Postal/ZIP Codes in Kusozu (長岡市) | 940-0085 |
| Postal/ZIP Codes in Machidamachi (長岡市) | 940-1111 |
| Postal/ZIP Codes in Maeda (長岡市) | 940-0042 |
| Postal/ZIP Codes in Maejimamachi (長岡市) | 940-1147 |
| Postal/ZIP Codes in Magariaramachi (長岡市) | 940-1103 |
| Postal/ZIP Codes in Akanuma (長岡市) | 954-0202 |