44 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Hermitage | 1 | 15,738 | 16,240 | -0.64% | 534 | 29 | City |
| Sharon | 2 | 12,647 | 13,131 | -0.76% | 3,353 | 4 | City |
| Grove City | 3 | 7,717 | 7,877 | -0.41% | 2,862 | 3 | Borough |
| Greenville | 4 | 5,440 | 5,533 | -0.35% | 2,883 | 2 | Borough |
| Pine | 5 | 4,701 | 4,804 | -0.4% | 185 | 25 | Township |
| Farrell | 6 | 4,113 | 4,257 | -0.7% | 1,817 | 2 | City |
| Sharpsville | 7 | 4,097 | 4,247 | -0.73% | 2,945 | 1 | Borough |
| Hempfield | 8 | 3,616 | 3,721 | -0.44% | 256 | 14 | Township |
| Shenango | 9 | 3,402 | 3,511 | -0.53% | 114 | 30 | Township |
| West Salem | 10 | 3,185 | 3,219 | -0.09% | 86 | 37 | Township |
| Pymatuning | 11 | 2,996 | 3,112 | -0.66% | 185 | 16 | Township |
| Findley | 12 | 2,805 | 2,846 | 2.82% | 132 | 21 | Township |
| South Pymatuning | 13 | 2,563 | 2,648 | -0.54% | 131 | 20 | Township |
| Lackawannock | 14 | 2,447 | 2,477 | -0.37% | 117 | 21 | Township |
| Delaware | 15 | 2,049 | 2,085 | -0.29% | 63 | 33 | Township |
| Mercer | 16 | 1,907 | 1,982 | -0.78% | 1,648 | 1 | Borough |
| East Lackawannock | 17 | 1,631 | 1,669 | -0.55% | 76 | 21 | Township |
| Wilmington | 18 | 1,424 | 1,408 | 0.49% | 109 | 13 | Township |
| Perry | 19 | 1,289 | 1,328 | -0.31% | 72 | 18 | Township |
| Sandy Lake | 20 | 1,188 | 1,196 | 0.17% | 49 | 24 | Township |
| Greene | 21 | 1,031 | 1,051 | -0.1% | 47 | 22 | Township |
| Mercer | 22 | 988 | 1,008 | -1% | 76 | 13 | Township |
| Stoneboro | 23 | 917 | 946 | -0.65% | 324 | 3 | Borough |
| Worth | 24 | 802 | 823 | -0.25% | 32 | 25 | Township |
| West Middlesex | 25 | 787 | 819 | -0.88% | 931 | 1 | Borough |
| Sandy Creek | 26 | 786 | 802 | -0.13% | 50 | 16 | Township |
| Sharon | 27 | 768 | 786 | -0.13% | 23 | 34 | Township |
| Greenville | 28 | 740 | 754 | -0.67% | 30 | 25 | Township |
| Salem | 29 | 734 | 751 | -0.14% | 55 | 13 | Township |
| Wolf Creek | 30 | 696 | 708 | -0.14% | 41 | 17 | Township |
| French Creek | 31 | 694 | 709 | -0.57% | 33 | 21 | Township |
| Lake | 32 | 684 | 703 | -0.58% | 42 | 16 | Township |
| Lake Latonka | 33 | 652 | 756 | -3.55% | 326 | 2 | CDP |
| Sandy Lake | 34 | 625 | 648 | -0.79% | 751 | 1 | Borough |
| Wheatland | 35 | 562 | 582 | -0.71% | 644 | 1 | Borough |
| Jamestown | 36 | 561 | 576 | -0.53% | 673 | 1 | Borough |
| Clark | 37 | 555 | 575 | -0.72% | 184 | 3 | Borough |
| Otter Creek | 38 | 508 | 524 | -0.39% | 43 | 12 | Township |
| New Vernon | 39 | 480 | 491 | -0.41% | 32 | 15 | Township |
| Deer Creek | 40 | 441 | 455 | -0.45% | 30 | 15 | Township |
| Fredonia | 41 | 417 | 434 | -0.95% | 1,168 | 0 | Borough |
| New Lebanon | 42 | 188 | 185 | 0% | 148 | 1 | Borough |
| Jackson Center | 43 | 184 | 192 | -1.08% | 162 | 1 | Borough |
| Sheakleyville | 44 | 145 | 150 | -0.68% | 740 | 0 | Borough |
Hermitage is the largest city in Mercer County, with a population of 15,738.
Sheakleyville is the smallest city in Mercer County, with a population of 145.
There are 44 cities in Mercer County, Pennsylvania.