31 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Hermitage | 1 | 15,709 | 16,243 | -0.68% | 533 | 29.46 | City |
| Sharon | 2 | 12,602 | 13,129 | -0.83% | 3,341 | 3.77 | City |
| Grove City | 3 | 7,715 | 7,875 | -0.41% | 2,862 | 2.70 | Borough |
| Greenville | 4 | 5,450 | 5,534 | -0.31% | 2,888 | 1.89 | Borough |
| Pine township | 5 | 4,656 | 4,794 | -0.77% | 183 | 25.41 | Township |
| Farrell | 6 | 4,098 | 4,253 | -0.75% | 1,810 | 2.26 | City |
| Sharpsville | 7 | 4,079 | 4,248 | -0.83% | 2,932 | 1.39 | Borough |
| Hempfield township | 8 | 3,597 | 3,727 | -0.74% | 254 | 14.15 | Township |
| Shenango township | 9 | 3,378 | 3,516 | -0.94% | 113 | 29.95 | Township |
| West Salem township | 10 | 3,122 | 3,213 | -0.95% | 85 | 36.88 | Township |
| Findley township | 11 | 3,010 | 2,845 | 6.36% | 142 | 21.22 | Township |
| Pymatuning township | 12 | 2,968 | 3,111 | -1.03% | 184 | 16.16 | Township |
| South Pymatuning township | 13 | 2,552 | 2,650 | -0.82% | 130 | 19.57 | Township |
| Lackawannock township | 14 | 2,469 | 2,478 | 0.12% | 118 | 20.92 | Township |
| Delaware township | 15 | 2,036 | 2,086 | -0.63% | 62 | 32.68 | Township |
| Mercer | 16 | 1,900 | 1,982 | -0.83% | 1,642 | 1.16 | Borough |
| East Lackawannock township | 17 | 1,633 | 1,670 | -0.55% | 76 | 21.40 | Township |
| Wilmington township | 18 | 1,422 | 1,407 | 0.5% | 109 | 13.05 | Township |
| Perry township | 19 | 1,279 | 1,331 | -0.85% | 71 | 18 | Township |
| Sandy Lake township | 20 | 1,174 | 1,196 | -0.42% | 48 | 24.38 | Township |
| Greene township | 21 | 1,019 | 1,053 | -0.78% | 47 | 21.83 | Township |
| Stoneboro | 22 | 919 | 948 | -0.65% | 324 | 2.83 | Borough |
| West Middlesex | 23 | 780 | 815 | -0.89% | 923 | 0.84 | Borough |
| Sandy Lake | 24 | 623 | 648 | -0.8% | 749 | 0.83 | Borough |
| Jamestown | 25 | 562 | 581 | -0.71% | 675 | 0.83 | Borough |
| Wheatland | 26 | 560 | 582 | -0.71% | 641 | 0.87 | Borough |
| Clark | 27 | 553 | 575 | -0.72% | 184 | 3.01 | Borough |
| Fredonia | 28 | 419 | 434 | -0.71% | 1,174 | 0.36 | Borough |
| New Lebanon | 29 | 185 | 185 | 0% | 145 | 1.27 | Borough |
| Jackson Center | 30 | 183 | 192 | -1.08% | 161 | 1.14 | Borough |
| Sheakleyville | 31 | 143 | 150 | -0.69% | 730 | 0.20 | Borough |
Hermitage is the largest city in Mercer County, with a population of 15,709.
Sheakleyville is the smallest city in Mercer County.
There are 31 cities in Mercer County, Pennsylvania.