Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Wilmington | 1 | 71,954 | 70,837 | 0.39% | 6,604 | 10.9 | City |
| Newark | 2 | 30,025 | 30,599 | -0.48% | 3,169 | 9.5 | City |
| Middletown | 3 | 25,567 | 23,386 | 2.18% | 2,017 | 12.7 | Town |
| Bear | 4 | 23,686 | 21,397 | 1.32% | 4,095 | 5.8 | CDP |
| Glasgow | 5 | 15,589 | 15,399 | 0.59% | 1,571 | 9.9 | CDP |
| Brookside | 6 | 14,327 | 13,741 | -0.01% | 3,691 | 3.9 | CDP |
| Hockessin | 7 | 13,936 | 14,172 | 0.21% | 1,388 | 10.0 | CDP |
| Pike Creek Valley | 8 | 11,491 | 11,346 | 0.17% | 4,002 | 2.9 | CDP |
| Claymont | 9 | 10,514 | 9,343 | 1.57% | 4,888 | 2.2 | CDP |
| North Star | 10 | 8,435 | 7,546 | 0.39% | 1,240 | 6.8 | CDP |
| Wilmington Manor | 11 | 8,322 | 8,335 | 0.37% | 5,093 | 1.6 | CDP |
| Pike Creek | 12 | 6,821 | 6,987 | -1.12% | 2,537 | 2.7 | CDP |
| Edgemoor | 13 | 6,620 | 6,483 | 1.04% | 3,452 | 1.9 | CDP |
| Elsmere | 14 | 6,134 | 6,224 | -0.37% | 6,215 | 1.0 | Town |
| New Castle | 15 | 5,552 | 5,540 | 0.05% | 1,596 | 3.5 | City |
| Greenville | 16 | 2,907 | 2,448 | 1.43% | 1,040 | 2.8 | CDP |
| Townsend | 17 | 2,861 | 2,744 | 1.02% | 2,699 | 1.1 | Town |
| Delaware City | 18 | 1,911 | 1,885 | 0.32% | 1,027 | 1.9 | City |
| St. Georges | 19 | 1,521 | 1,045 | 7.64% | 1,103 | 1.4 | CDP |
| Bellefonte | 20 | 1,235 | 1,225 | 0.16% | 6,977 | 0.2 | Town |
| Newport | 21 | 892 | 908 | -0.45% | 1,910 | 0.5 | Town |
| Arden | 22 | 434 | 429 | 0.23% | 1,743 | 0.2 | Village |
| Odessa | 23 | 362 | 369 | -0.55% | 714 | 0.5 | Town |
| Ardentown | 24 | 254 | 253 | 0% | 1,085 | 0.2 | Village |
| Ardencroft | 25 | 229 | 227 | 0% | 2,573 | 0.1 | Village |
| Port Penn | 26 | 161 | 293 | 7.33% | 399 | 0.4 | CDP |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Wilmington is the largest city in New Castle County.
Port Penn is the smallest city in New Castle County.
There are 26 cities in New Castle County, Delaware.