| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Coal | 1 | 9,808 | 10,126 | 0.89% | 373 | 26 | Township |
| Sunbury | 2 | 9,452 | 9,698 | -0.45% | 4,710 | 2 | City |
| Shamokin | 3 | 6,725 | 6,943 | -0.58% | 8,152 | 1 | City |
| Milton | 4 | 6,424 | 6,610 | -0.51% | 1,852 | 3 | Borough |
| Mount Carmel | 5 | 5,550 | 5,713 | -0.52% | 8,384 | 1 | Borough |
| Delaware | 6 | 4,282 | 4,308 | -0.12% | 142 | 30 | Township |
| Ralpho | 7 | 4,187 | 4,186 | 0.14% | 227 | 18 | Township |
| Point | 8 | 3,812 | 3,847 | -0.16% | 152 | 25 | Township |
| Northumberland | 9 | 3,781 | 3,885 | -0.5% | 2,348 | 2 | Borough |
| Kulpmont | 10 | 2,673 | 2,757 | -0.56% | 2,787 | 1 | Borough |
| West Chillisquaque | 11 | 2,614 | 2,598 | 0% | 203 | 13 | Township |
| Mount Carmel | 12 | 2,464 | 2,506 | -0.2% | 114 | 22 | Township |
| Shamokin | 13 | 2,448 | 2,380 | 0.74% | 79 | 31 | Township |
| Upper Augusta | 14 | 2,436 | 2,471 | 0.16% | 122 | 20 | Township |
| Rockefeller | 15 | 2,296 | 2,349 | -0.26% | 111 | 21 | Township |
| Watsontown | 16 | 2,180 | 2,227 | -0.37% | 3,075 | 1 | Borough |
| Riverside | 17 | 1,982 | 2,031 | -0.45% | 401 | 5 | Borough |
| Lewis | 18 | 1,931 | 1,938 | 0.16% | 73 | 26 | Township |
| Turbot | 19 | 1,791 | 1,807 | -0.17% | 130 | 14 | Township |
| Zerbe | 20 | 1,765 | 1,805 | -0.23% | 160 | 11 | Township |
| Lower Mahanoy | 21 | 1,601 | 1,627 | -0.12% | 73 | 22 | Township |
| Rush | 22 | 1,163 | 1,193 | -0.26% | 44 | 27 | Township |
| Lower Augusta | 23 | 1,034 | 1,041 | 0.39% | 57 | 18 | Township |
| Jordan | 24 | 764 | 783 | -0.26% | 44 | 17 | Township |
| East Chillisquaque | 25 | 659 | 671 | 0% | 82 | 8 | Township |
| Turbotville | 26 | 656 | 679 | -0.61% | 1,455 | 0 | Borough |
| Upper Mahanoy | 27 | 639 | 647 | 0.16% | 27 | 23 | Township |
| East Cameron | 28 | 619 | 624 | -0.32% | 53 | 12 | Township |
| Marion Heights | 29 | 550 | 562 | -0.36% | 3,595 | 0 | Borough |
| West Cameron | 30 | 495 | 493 | 0.61% | 42 | 12 | Township |
| Little Mahanoy | 31 | 432 | 427 | 0.23% | 40 | 11 | Township |
| Herndon | 32 | 338 | 351 | -0.88% | 427 | 1 | Borough |
| Snydertown | 33 | 314 | 323 | -0.63% | 91 | 3 | Borough |
| McEwensville | 34 | 283 | 286 | -0.35% | 2,419 | 0 | Borough |
Coal is the largest city in Northumberland County, with a population of 9,808.
McEwensville is the smallest city in Northumberland County, with a population of 283.
There are 34 cities in Northumberland County, Pennsylvania.