10 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Pasco | 1 | 82,733 | 77,345 | 1.23% | 2,123 | 39 | City |
| Pasco | 2 | 82,733 | 77,686 | 1.23% | 2,123 | 39 | City |
| Connell | 3 | 4,978 | 5,438 | -1.83% | 669 | 7 | City |
| Connell | 4 | 4,978 | 5,443 | -1.83% | 669 | 7 | City |
| Basin City | 5 | 1,689 | 1,173 | 2.36% | 530 | 3 | CDP |
| West Pasco | 6 | 1,403 | 1,592 | -9.95% | 960 | 1 | CDP |
| Mesa | 7 | 388 | 386 | 0% | 234 | 2 | City |
| Mesa | 8 | 388 | 386 | 0% | 234 | 2 | City |
| Kahlotus | 9 | 140 | 143 | -0.71% | 368 | 0 | City |
| Kahlotus | 10 | 140 | 143 | -0.71% | 368 | 0 | City |
Pasco is the largest city in Franklin County, with a population of 82,733.
Kahlotus is the smallest city in Franklin County, with a population of 140.
There are 10 cities in Franklin County, Washington.