33 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 6360 | Norwich | 37,219 |
| 6340 | Groton | 29,672 |
| 6320 | New London | 27,600 |
| 6226 | Willimantic | 19,103 |
| 6415 | Colchester | 16,130 |
| 6385 | Waterford | 15,886 |
| 6351 | Jewett City | 15,695 |
| 6355 | Mystic | 12,481 |
| 6357 | Niantic | 11,530 |
| 6382 | Uncasville | 10,240 |
| 6339 | Ledyard | 9,239 |
| 6379 | Pawcatuck | 8,973 |
| 6370 | Oakdale | 7,839 |
| 6249 | Lebanon | 7,145 |
| 6333 | East Lyme | 7,070 |
| 6335 | Gales Ferry | 6,199 |
| 6378 | Stonington | 5,488 |
| 6359 | North Stonington | 5,160 |
| 6365 | Preston | 4,719 |
| 6420 | Salem | 4,307 |
| 6375 | Quaker Hill | 3,696 |
| 6280 | Windham | 3,337 |
| 6330 | Baltic | 3,305 |
| 6380 | Taftville | 2,725 |
| 6334 | Bozrah | 2,343 |
| 6256 | North Windham | 2,273 |
| 6254 | North Franklin | 1,892 |
| 6266 | South Windham | 227 |
| 6389 | Yantic | 110 |
| 6350 | Hanover | 82 |
| 6353 | Montville | 75 |
| 6336 | Gilman | 67 |
| 6338 | Mashantucket | 41 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 33 ZCTAs in Southeastern CT Planning Region, Connecticut (US Census).