26 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Wilmington | 1 | 72,233 | 70,837 | 0.39% | 6,630 | 10.89 | City |
| Newark | 2 | 29,882 | 30,599 | -0.48% | 3,154 | 9.47 | City |
| Middletown | 3 | 26,112 | 23,386 | 2.13% | 2,060 | 12.68 | Town |
| Bear | 4 | 23,995 | 21,397 | 1.3% | 4,149 | 5.78 | CDP |
| Glasgow | 5 | 15,681 | 15,399 | 0.59% | 1,580 | 9.93 | CDP |
| Brookside | 6 | 14,325 | 13,741 | -0.01% | 3,690 | 3.88 | CDP |
| Hockessin | 7 | 13,966 | 14,172 | 0.22% | 1,391 | 10.04 | CDP |
| Pike Creek Valley | 8 | 11,511 | 11,346 | 0.17% | 4,009 | 2.87 | CDP |
| Claymont | 9 | 10,676 | 9,343 | 1.54% | 4,963 | 2.15 | CDP |
| North Star | 10 | 8,468 | 7,546 | 0.39% | 1,245 | 6.80 | CDP |
| Wilmington Manor | 11 | 8,353 | 8,335 | 0.37% | 5,112 | 1.63 | CDP |
| Pike Creek | 12 | 6,744 | 6,987 | -1.13% | 2,508 | 2.69 | CDP |
| Edgemoor | 13 | 6,687 | 6,483 | 1.01% | 3,486 | 1.92 | CDP |
| Elsmere | 14 | 6,112 | 6,224 | -0.36% | 6,193 | 0.99 | Town |
| New Castle | 15 | 5,555 | 5,540 | 0.05% | 1,597 | 3.48 | City |
| Greenville | 16 | 2,948 | 2,448 | 1.41% | 1,054 | 2.80 | CDP |
| Townsend | 17 | 2,890 | 2,744 | 1.01% | 2,726 | 1.06 | Town |
| Delaware City | 18 | 1,918 | 1,885 | 0.37% | 1,031 | 1.86 | City |
| St. Georges | 19 | 1,630 | 1,045 | 7.17% | 1,182 | 1.38 | CDP |
| Bellefonte | 20 | 1,238 | 1,225 | 0.24% | 6,994 | 0.18 | Town |
| Newport | 21 | 888 | 908 | -0.45% | 1,901 | 0.47 | Town |
| Arden | 22 | 435 | 429 | 0.23% | 1,747 | 0.25 | Village |
| Odessa | 23 | 360 | 369 | -0.55% | 710 | 0.51 | Town |
| Ardentown | 24 | 254 | 253 | 0% | 1,085 | 0.23 | Village |
| Ardencroft | 25 | 230 | 227 | 0.44% | 2,584 | 0.09 | Village |
| Port Penn | 26 | 172 | 293 | 6.83% | 426 | 0.40 | CDP |
Wilmington is the largest city in New Castle County, with a population of 72,233.
Port Penn is the smallest city in New Castle County.
There are 26 cities in New Castle County, Delaware.