21 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Susanville | 1 | 10,197 | 16,426 | -10.89% | 1,288 | 8 | City |
| Janesville | 2 | 2,949 | 2,803 | 3.62% | 87 | 34 | CDP |
| Herlong | 3 | 1,525 | 1,272 | 5.61% | 914 | 2 | CDP |
| Johnstonville | 4 | 1,106 | 1,151 | 0.45% | 129 | 9 | CDP |
| Doyle | 5 | 1,078 | 745 | 2.57% | 176 | 6 | CDP |
| Westwood | 6 | 983 | 1,387 | -4.38% | 177 | 6 | CDP |
| Patton Village | 7 | 814 | 635 | 0.87% | 233 | 3 | CDP |
| Lake Almanor Country Club | 8 | 556 | 429 | 1.65% | 203 | 3 | CDP |
| McArthur | 9 | 447 | 521 | 1.59% | 447 | 1 | CDP |
| Hamilton Branch | 10 | 433 | 446 | -1.59% | 399 | 1 | CDP |
| Chilcoot-Vinton | 11 | 354 | 340 | -1.94% | 27 | 13 | CDP |
| Clear Creek | 12 | 342 | 293 | 3.64% | 302 | 1 | CDP |
| Lake Almanor Peninsula | 13 | 310 | 382 | -0.96% | 102 | 3 | CDP |
| Spaulding | 14 | 247 | 129 | 2.07% | 74 | 3 | CDP |
| East Shore | 15 | 222 | 139 | 1.83% | 188 | 1 | CDP |
| Stones Landing | 16 | 180 | 102 | 7.14% | 85 | 2 | CDP |
| Litchfield | 17 | 119 | 183 | -4.03% | 30 | 4 | CDP |
| Bieber | 18 | 111 | 145 | -10.48% | 32 | 3 | CDP |
| Nubieber | 19 | 52 | 31 | 6.12% | 69 | 1 | CDP |
| Madeline | 20 | 39 | 11 | 8.33% | 736 | 0 | CDP |
| Little Valley | 21 | 13 | 19 | 8.33% | 31 | 0 | CDP |
Susanville is the largest city in Lassen County, with a population of 10,197.
Little Valley is the smallest city in Lassen County, with a population of 13.
There are 21 cities in Lassen County, California.