17 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Dover | 1 | 34,315 | 32,783 | 1.2% | 1,284 | 27 | City |
| Dover | 2 | 34,190 | 32,783 | 0.83% | 1,279 | 27 | City |
| Rochester | 3 | 33,867 | 32,521 | 0.8% | 752 | 45 | City |
| Rochester | 4 | 33,673 | 32,521 | 0.22% | 748 | 45 | City |
| Durham | 5 | 15,249 | 15,557 | -0.14% | 680 | 22 | Town |
| Somersworth | 6 | 12,291 | 11,925 | 0.6% | 1,254 | 10 | City |
| Somersworth | 7 | 12,247 | 11,925 | 0.24% | 1,250 | 10 | City |
| Barrington | 8 | 9,704 | 9,320 | 0.78% | 208 | 47 | Town |
| Farmington | 9 | 6,784 | 6,708 | -0.32% | 185 | 37 | Town |
| Lee | 10 | 4,581 | 4,525 | -0.11% | 229 | 20 | Town |
| Milton | 11 | 4,580 | 4,474 | 0.17% | 139 | 33 | Town |
| Strafford | 12 | 4,343 | 4,236 | 0.09% | 89 | 49 | Town |
| New Durham | 13 | 2,842 | 2,699 | 1% | 69 | 41 | Town |
| Rollinsford | 14 | 2,673 | 2,592 | 0.53% | 367 | 7 | Town |
| Madbury | 15 | 1,942 | 1,911 | -0.15% | 167 | 12 | Town |
| Middleton | 16 | 1,863 | 1,823 | 0.32% | 103 | 18 | Town |
| Newington | 17 | 848 | 816 | 1.31% | 105 | 8 | Town |
Dover is the largest city in Strafford County, with a population of 34,315.
Newington is the smallest city in Strafford County, with a population of 848.
There are 17 cities in Strafford County, New Hampshire.