| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Dover | 1 | 35,343 | 32,790 | 2.08% | 1,322 | 27 | City |
| Rochester | 2 | 33,851 | 32,514 | 0.4% | 752 | 45 | City |
| Durham | 3 | 15,272 | 15,564 | -0.48% | 681 | 22 | Town |
| Somersworth | 4 | 12,126 | 11,933 | -0.37% | 1,237 | 10 | City |
| Barrington | 5 | 9,677 | 9,324 | 0.36% | 207 | 47 | Town |
| Farmington | 6 | 6,729 | 6,707 | -0.77% | 184 | 37 | Town |
| Milton | 7 | 4,543 | 4,474 | -0.42% | 137 | 33 | Town |
| Lee | 8 | 4,534 | 4,529 | -0.64% | 227 | 20 | Town |
| Strafford | 9 | 4,326 | 4,244 | -0.28% | 88 | 49 | Town |
| New Durham | 10 | 2,969 | 2,699 | 2.73% | 72 | 41 | Town |
| Rollinsford | 11 | 2,603 | 2,578 | -0.69% | 357 | 7 | Town |
| Madbury | 12 | 1,908 | 1,910 | -0.99% | 164 | 12 | Town |
| Middleton | 13 | 1,874 | 1,818 | 0.59% | 104 | 18 | Town |
| Newington | 14 | 856 | 816 | 1.06% | 106 | 8 | Town |
Dover is the largest city in Strafford County, with a population of 35,343.
Newington is the smallest city in Strafford County, with a population of 856.
There are 14 cities in Strafford County, New Hampshire.