| Locality | Postal Code |
|---|---|
| Postal/ZIP Codes in Suikawakoji (一関市) | 021-0841 |
| Postal/ZIP Codes in Takasakicho (一関市) | 021-0875 |
| Postal/ZIP Codes in Takeyamacho (一関市) | 021-0027 |
| Postal/ZIP Codes in Takizawa (一関市) | 029-0132 |
| Postal/ZIP Codes in Tammachi (一関市) | 021-0844 |
| Postal/ZIP Codes in Tamuracho (一関市) | 021-0885 |
| Postal/ZIP Codes in Tsuriyama (一関市) | 021-0874 |
| Postal/ZIP Codes in Unan (一関市) | 021-0834 |
| Postal/ZIP Codes in Yahata. Yamanosawa (一関市) | 021-0102 |
| Postal/ZIP Codes in Yamanome (一関市) | 021 |
| Postal/ZIP Codes in Yamanomemachi (一関市) | 021-0011 |
| Postal/ZIP Codes in Yanagimachi (一関市) | 021-0842 |
| Postal/ZIP Codes in Yasakae (一関市) | 029-0211 |
| Postal/ZIP Codes in Yogai (一関市) | 021-0815 |
| Postal/ZIP Codes in Yutakamachi (一関市) | 021-0805 |
| Postal/ZIP Codes in Zaka. Sangatsuda. Shimotsuno. Shimohon (一関市) | 021-0102 |