33 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 06360 | Norwich | 37,527 |
| 06340 | Groton | 29,833 |
| 06320 | New London | 27,275 |
| 06226 | Willimantic | 19,068 |
| 06415 | Colchester | 16,075 |
| 06385 | Waterford | 15,900 |
| 06351 | Jewett City | 15,697 |
| 06355 | Mystic | 12,223 |
| 06357 | Niantic | 11,315 |
| 06382 | Uncasville | 10,076 |
| 06339 | Ledyard | 9,263 |
| 06379 | Pawcatuck | 9,003 |
| 06370 | Oakdale | 7,547 |
| 06333 | East Lyme | 7,323 |
| 06249 | Lebanon | 7,137 |
| 06335 | Gales Ferry | 6,100 |
| 06378 | Stonington | 5,408 |
| 06359 | North Stonington | 5,154 |
| 06365 | Preston | 4,781 |
| 06420 | Salem | 4,323 |
| 06375 | Quaker Hill | 3,667 |
| 06330 | Baltic | 3,311 |
| 06280 | Windham | 3,179 |
| 06380 | Taftville | 2,427 |
| 06334 | Bozrah | 2,327 |
| 06254 | North Franklin | 1,925 |
| 06256 | North Windham | 1,796 |
| 06353 | Montville | 369 |
| 06266 | South Windham | 278 |
| 06350 | Hanover | 71 |
| 06338 | Mashantucket | 62 |
| 06336 | Gilman | 46 |
| 06389 | Yantic | 38 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 33 ZCTAs in Southeastern CT Planning Region, Connecticut (US Census).