21 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rochester city | 1 | 34,305 | 32,517 | 1.16% | 762 | 45.02 | City |
| Rochester | 2 | 34,187 | 32,517 | 0.99% | 759 | 45.02 | City |
| Dover | 3 | 33,957 | 32,776 | 0.7% | 1,270 | 26.73 | City |
| Dover city | 4 | 33,705 | 32,776 | 0.33% | 1,261 | 26.73 | City |
| Durham town | 5 | 14,917 | 15,554 | -0.01% | 666 | 22.41 | Town |
| Somersworth | 6 | 12,367 | 11,929 | 0.72% | 1,262 | 9.80 | City |
| Somersworth city | 7 | 12,286 | 11,929 | 0.38% | 1,254 | 9.80 | City |
| Durham | 8 | 10,900 | 12,016 | 0.34% | 3,603 | 3.02 | CDP |
| Barrington town | 9 | 9,654 | 9,320 | 0.52% | 207 | 46.65 | Town |
| Farmington town | 10 | 6,850 | 6,711 | 0.06% | 187 | 36.59 | Town |
| Lee town | 11 | 4,616 | 4,527 | 0.2% | 231 | 19.99 | Town |
| Milton town | 12 | 4,564 | 4,472 | 0% | 138 | 33.05 | Town |
| Strafford town | 13 | 4,359 | 4,235 | 0.3% | 89 | 49.03 | Town |
| Farmington | 14 | 3,681 | 4,140 | -0.38% | 588 | 6.26 | CDP |
| New Durham town | 15 | 2,847 | 2,696 | 1.1% | 69 | 41.22 | Town |
| Rollinsford town | 16 | 2,676 | 2,593 | 0.53% | 367 | 7.29 | Town |
| Madbury town | 17 | 1,953 | 1,915 | 0.05% | 168 | 11.62 | Town |
| Middleton town | 18 | 1,855 | 1,823 | 0.11% | 103 | 18.07 | Town |
| Newington town | 19 | 831 | 813 | 0.48% | 102 | 8.11 | Town |
| Milton | 20 | 293 | 537 | -5.79% | 363 | 0.81 | CDP |
| Milton Mills | 21 | 77 | 216 | -15.38% | 89 | 0.86 | CDP |
Rochester city is the largest city in Strafford County, with a population of 34,305.
Milton Mills is the smallest city in Strafford County.
There are 21 cities in Strafford County, New Hampshire.