42 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Hermitage | 1 | 15,638 | 16,240 | -0.64% | 516 | 30 | City |
| Sharon | 2 | 12,550 | 13,131 | -0.77% | 3,327 | 4 | City |
| Grove City | 3 | 7,685 | 7,877 | -0.41% | 2,851 | 3 | Borough |
| Greenville | 4 | 5,422 | 5,533 | -0.33% | 2,873 | 2 | Borough |
| Pine | 5 | 4,682 | 4,804 | -0.4% | 184 | 25 | Township |
| Farrell | 6 | 4,084 | 4,257 | -0.71% | 1,804 | 2 | City |
| Sharpsville | 7 | 4,067 | 4,247 | -0.73% | 2,924 | 1 | Borough |
| Hempfield | 8 | 3,600 | 3,721 | -0.44% | 254 | 14 | Township |
| Shenango | 9 | 3,384 | 3,511 | -0.53% | 113 | 30 | Township |
| West Salem | 10 | 3,182 | 3,219 | -0.09% | 86 | 37 | Township |
| Pymatuning | 11 | 2,976 | 3,112 | -0.67% | 184 | 16 | Township |
| Findley | 12 | 2,882 | 2,846 | 2.75% | 136 | 21 | Township |
| South Pymatuning | 13 | 2,549 | 2,648 | -0.55% | 130 | 20 | Township |
| Lackawannock | 14 | 2,438 | 2,477 | -0.37% | 117 | 21 | Township |
| Delaware | 15 | 2,043 | 2,085 | -0.29% | 63 | 33 | Township |
| Mercer | 16 | 1,892 | 1,982 | -0.79% | 1,635 | 1 | Borough |
| East Lackawannock | 17 | 1,622 | 1,669 | -0.55% | 76 | 21 | Township |
| Wilmington | 18 | 1,431 | 1,408 | 0.49% | 110 | 13 | Township |
| Perry | 19 | 1,285 | 1,328 | -0.31% | 71 | 18 | Township |
| Sandy Lake | 20 | 1,190 | 1,196 | 0.17% | 49 | 24 | Township |
| Greene | 21 | 1,030 | 1,051 | -0.1% | 47 | 22 | Township |
| Mercer | 22 | 978 | 1,008 | -1.01% | 75 | 13 | Township |
| Stoneboro | 23 | 911 | 946 | -0.65% | 321 | 3 | Borough |
| Worth | 24 | 800 | 823 | -0.25% | 32 | 25 | Township |
| Sandy Creek | 25 | 785 | 802 | -0.13% | 50 | 16 | Township |
| West Middlesex | 26 | 781 | 819 | -0.76% | 924 | 1 | Borough |
| Sharon | 27 | 767 | 786 | -0.13% | 23 | 34 | Township |
| Greenville | 28 | 735 | 754 | -0.68% | 29 | 25 | Township |
| Salem | 29 | 733 | 751 | -0.14% | 55 | 13 | Township |
| Wolf Creek | 30 | 695 | 708 | -0.14% | 41 | 17 | Township |
| French Creek | 31 | 690 | 709 | -0.58% | 33 | 21 | Township |
| Lake | 32 | 680 | 703 | -0.58% | 42 | 16 | Township |
| Sandy Lake | 33 | 621 | 648 | -0.64% | 746 | 1 | Borough |
| Jamestown | 34 | 558 | 576 | -0.53% | 670 | 1 | Borough |
| Clark | 35 | 551 | 575 | -0.72% | 183 | 3 | Borough |
| Otter Creek | 36 | 506 | 524 | -0.39% | 43 | 12 | Township |
| New Vernon | 37 | 478 | 491 | -0.42% | 32 | 15 | Township |
| Deer Creek | 38 | 439 | 455 | -0.45% | 30 | 15 | Township |
| Fredonia | 39 | 414 | 434 | -0.72% | 1,160 | 0 | Borough |
| New Lebanon | 40 | 189 | 185 | 0.53% | 148 | 1 | Borough |
| Jackson Center | 41 | 183 | 192 | -0.54% | 161 | 1 | Borough |
| Sheakleyville | 42 | 144 | 150 | -0.69% | 735 | 0 | Borough |
Hermitage is the largest city in Mercer County, with a population of 15,638.
Sheakleyville is the smallest city in Mercer County, with a population of 144.
There are 42 cities in Mercer County, Pennsylvania.