28 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Coal township | 1 | 10,303 | 10,123 | 2.82% | 392 | 26.30 | Township |
| Sunbury | 2 | 9,429 | 9,704 | -0.58% | 4,698 | 2.01 | City |
| Shamokin | 3 | 6,718 | 6,930 | -0.62% | 8,143 | 0.82 | City |
| Milton | 4 | 6,418 | 6,615 | -0.6% | 1,850 | 3.47 | Borough |
| Mount Carmel | 5 | 5,573 | 5,727 | -0.55% | 8,418 | 0.66 | Borough |
| Delaware township | 6 | 4,269 | 4,298 | -0.02% | 142 | 30.10 | Township |
| Ralpho township | 7 | 4,185 | 4,186 | 0.12% | 227 | 18.46 | Township |
| Northumberland | 8 | 3,794 | 3,906 | -0.58% | 2,357 | 1.61 | Borough |
| Point township | 9 | 3,764 | 3,831 | -0.37% | 150 | 25.05 | Township |
| Kulpmont | 10 | 2,667 | 2,757 | -0.67% | 2,781 | 0.96 | Borough |
| West Chillisquaque township | 11 | 2,657 | 2,602 | 0.64% | 206 | 12.88 | Township |
| Mount Carmel township | 12 | 2,432 | 2,489 | -0.37% | 112 | 21.62 | Township |
| Upper Augusta township | 13 | 2,406 | 2,472 | -0.54% | 120 | 20.02 | Township |
| Shamokin township | 14 | 2,393 | 2,372 | 0.21% | 78 | 30.81 | Township |
| Rockefeller township | 15 | 2,291 | 2,359 | -0.61% | 111 | 20.62 | Township |
| Watsontown | 16 | 2,199 | 2,236 | -0.32% | 3,102 | 0.71 | Borough |
| Riverside | 17 | 1,995 | 2,040 | -0.45% | 404 | 4.94 | Borough |
| Lewis township | 18 | 1,912 | 1,938 | -0.36% | 72 | 26.43 | Township |
| Turbot township | 19 | 1,795 | 1,799 | 0.17% | 130 | 13.81 | Township |
| Zerbe township | 20 | 1,753 | 1,802 | -0.51% | 159 | 11.05 | Township |
| Lower Mahanoy township | 21 | 1,594 | 1,627 | -0.38% | 73 | 21.96 | Township |
| Rush township | 22 | 1,156 | 1,194 | -0.69% | 43 | 26.64 | Township |
| Lower Augusta township | 23 | 1,014 | 1,042 | -0.59% | 56 | 18.27 | Township |
| Turbotville | 24 | 655 | 677 | -0.61% | 1,452 | 0.45 | Borough |
| Marion Heights | 25 | 546 | 558 | -0.36% | 3,569 | 0.15 | Borough |
| Herndon | 26 | 340 | 350 | -0.58% | 430 | 0.79 | Borough |
| Snydertown | 27 | 318 | 328 | -0.63% | 93 | 3.43 | Borough |
| McEwensville | 28 | 288 | 290 | 0% | 2,462 | 0.12 | Borough |
Coal township is the largest city in Northumberland County, with a population of 10,303.
McEwensville is the smallest city in Northumberland County.
There are 28 cities in Northumberland County, Pennsylvania.