25 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Milford | 1 | 15,463 | 11,310 | 4.68% | 1,569 | 10 | City |
| Seaford | 2 | 9,437 | 7,982 | 2.64% | 1,849 | 5 | City |
| Georgetown | 3 | 8,550 | 7,193 | 2.72% | 1,703 | 5 | Town |
| Millsboro | 4 | 8,324 | 6,943 | 2.84% | 1,629 | 5 | Town |
| Laurel | 5 | 4,644 | 3,896 | 2.77% | 1,677 | 3 | Town |
| Milton | 6 | 3,992 | 3,335 | 2.83% | 1,499 | 3 | Town |
| Lewes | 7 | 3,893 | 3,320 | 2.53% | 929 | 4 | City |
| Selbyville | 8 | 3,474 | 2,907 | 2.81% | 857 | 4 | Town |
| Ocean View | 9 | 3,203 | 2,663 | 2.89% | 1,133 | 3 | Town |
| Bridgeville | 10 | 3,076 | 2,574 | 2.81% | 638 | 5 | Town |
| Delmar | 11 | 2,397 | 2,040 | 2.57% | 1,261 | 2 | Town |
| Millville | 12 | 2,233 | 1,857 | 2.9% | 877 | 3 | Town |
| Blades | 13 | 1,405 | 1,179 | 2.78% | 2,541 | 1 | Town |
| Rehoboth Beach | 14 | 1,328 | 1,115 | 2.79% | 1,130 | 1 | City |
| Greenwood | 15 | 1,187 | 994 | 2.77% | 1,495 | 1 | Town |
| Bethany Beach | 16 | 1,146 | 957 | 2.87% | 998 | 1 | Town |
| Dagsboro | 17 | 1,045 | 874 | 2.85% | 727 | 1 | Town |
| Frankford | 18 | 955 | 805 | 2.69% | 823 | 1 | Town |
| Ellendale | 19 | 587 | 493 | 2.8% | 402 | 1 | Town |
| South Bethany | 20 | 550 | 460 | 2.8% | 1,093 | 1 | Town |
| Dewey Beach | 21 | 428 | 358 | 2.88% | 1,293 | 0 | Town |
| Fenwick Island | 22 | 411 | 344 | 2.75% | 1,242 | 0 | Town |
| Bethel | 23 | 281 | 239 | 2.55% | 639 | 0 | Town |
| Henlopen Acres | 24 | 167 | 140 | 3.09% | 655 | 0 | Town |
| Galestown | 25 | 115 | 114 | 0% | 489 | 0 | Town |
Milford is the largest city in Sussex County, with a population of 15,463.
Galestown is the smallest city in Sussex County, with a population of 115.
There are 25 cities in Sussex County, Delaware.