| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Berlin | 1 | 9,492 | 9,409 | -0.11% | 155 | 61 | City |
| Lancaster | 2 | 3,217 | 3,214 | -0.03% | 64 | 50 | Town |
| Gorham | 3 | 2,649 | 2,693 | -0.45% | 83 | 32 | Town |
| Whitefield | 4 | 2,533 | 2,497 | -0.08% | 74 | 34 | Town |
| Colebrook | 5 | 2,115 | 2,082 | 0.24% | 52 | 41 | Town |
| Northumberland | 6 | 2,088 | 2,125 | -0.38% | 59 | 36 | Town |
| Milan | 7 | 1,348 | 1,360 | -0.44% | 21 | 64 | Town |
| Jefferson | 8 | 1,065 | 1,045 | 0.19% | 21 | 50 | Town |
| Dalton | 9 | 902 | 927 | -0.55% | 33 | 28 | Town |
| Pittsburg | 10 | 852 | 806 | 0.83% | 3.0 | 281 | Town |
| Carroll | 11 | 843 | 820 | 0.24% | 17 | 50 | Town |
| Stewartstown | 12 | 770 | 806 | -0.52% | 17 | 46 | Town |
| Columbia | 13 | 680 | 661 | 1.04% | 11 | 61 | Town |
| Stratford | 14 | 642 | 661 | -0.62% | 8.0 | 79 | Town |
| Stark | 15 | 460 | 474 | -0.65% | 8.0 | 59 | Town |
| Shelburne | 16 | 365 | 354 | 0.55% | 8.0 | 48 | Town |
| Randolph | 17 | 327 | 329 | 0% | 7.0 | 47 | Town |
| Dummer | 18 | 314 | 303 | 0.32% | 7.0 | 48 | Town |
| Errol | 19 | 289 | 299 | -0.69% | 5.0 | 60 | Town |
| Clarksville | 20 | 282 | 291 | -0.7% | 5.0 | 60 | Town |
Berlin is the largest city in Coos County, with a population of 9,492.
Clarksville is the smallest city in Coos County, with a population of 282.
There are 20 cities in Coos County, New Hampshire.