| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Milford | 1 | 15,417 | 11,296 | 4.71% | 1,564 | 10 | City |
| Seaford | 2 | 9,414 | 7,982 | 2.72% | 1,844 | 5 | City |
| Georgetown | 3 | 8,517 | 7,220 | 2.73% | 1,696 | 5 | Town |
| Millsboro | 4 | 8,116 | 6,817 | 2.86% | 1,588 | 5 | Town |
| Laurel | 5 | 4,684 | 3,957 | 2.79% | 1,691 | 3 | Town |
| Milton | 6 | 3,970 | 3,339 | 2.85% | 1,491 | 3 | Town |
| Lewes | 7 | 3,924 | 3,355 | 2.56% | 936 | 4 | City |
| Selbyville | 8 | 3,478 | 2,920 | 2.87% | 858 | 4 | Town |
| Ocean View | 9 | 3,196 | 2,682 | 2.86% | 1,130 | 3 | Town |
| Bridgeville | 10 | 3,083 | 2,590 | 2.87% | 639 | 5 | Town |
| Delmar | 11 | 2,427 | 2,071 | 2.58% | 1,277 | 2 | Town |
| Millville | 12 | 2,207 | 1,847 | 2.89% | 867 | 3 | Town |
| Blades | 13 | 1,409 | 1,192 | 2.7% | 2,548 | 1 | Town |
| Rehoboth Beach | 14 | 1,345 | 1,135 | 2.75% | 1,145 | 1 | City |
| Greenwood | 15 | 1,186 | 997 | 2.86% | 1,494 | 1 | Town |
| Bethany Beach | 16 | 1,135 | 955 | 2.81% | 989 | 1 | Town |
| Dagsboro | 17 | 1,011 | 851 | 2.85% | 703 | 1 | Town |
| Frankford | 18 | 961 | 807 | 2.78% | 828 | 1 | Town |
| Ellendale | 19 | 608 | 510 | 2.88% | 416 | 1 | Town |
| South Bethany | 20 | 553 | 465 | 2.79% | 1,099 | 1 | Town |
| Dewey Beach | 21 | 428 | 360 | 2.88% | 1,293 | 0 | Town |
| Fenwick Island | 22 | 409 | 344 | 2.76% | 1,236 | 0 | Town |
| Bethel | 23 | 281 | 239 | 2.55% | 639 | 0 | Town |
| Henlopen Acres | 24 | 163 | 138 | 2.52% | 639 | 0 | Town |
| Galestown | 25 | 117 | 113 | 0% | 498 | 0 | Town |
Milford is the largest city in Sussex County, with a population of 15,417.
Galestown is the smallest city in Sussex County, with a population of 117.
There are 25 cities in Sussex County, Delaware.