Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Butler township | 1 | 16,783 | 17,230 | -0.2% | 776 | 21.6 | Township |
| Adams township | 2 | 15,879 | 14,854 | 1.77% | 711 | 22.3 | Township |
| Butler | 3 | 12,970 | 13,484 | -0.98% | 4,770 | 2.7 | City |
| Butler township | 4 | 10,035 | 9,504 | 0.96% | 298 | 33.6 | Township |
| Slippery Rock township | 5 | 8,409 | 6,712 | -0.2% | 326 | 25.8 | Township |
| Buffalo township | 6 | 8,237 | 7,925 | 1.05% | 341 | 24.1 | Township |
| Center township | 7 | 7,817 | 7,892 | 0.09% | 321 | 24.4 | Township |
| Middlesex township | 8 | 7,420 | 6,889 | 0.61% | 321 | 23.1 | Township |
| Butler township | 9 | 5,044 | 4,905 | 0.92% | 194 | 26.0 | Township |
| Summit township | 10 | 4,376 | 4,500 | -0.46% | 195 | 22.4 | Township |
| Connoquenessing township | 11 | 4,176 | 4,258 | 0.26% | 184 | 22.7 | Township |
| Zelienople | 12 | 3,753 | 3,905 | -1% | 1,828 | 2.1 | Borough |
| Slippery Rock | 13 | 3,716 | 3,168 | 3.83% | 2,259 | 1.6 | Borough |
| Forward township | 14 | 3,364 | 3,206 | 0.72% | 146 | 23.0 | Township |
| Harmony township | 15 | 3,108 | 3,188 | -0.35% | 1,068 | 2.9 | Township |
| Slippery Rock township | 16 | 2,873 | 2,912 | -0.21% | 97 | 29.7 | Township |
| Oakland township | 17 | 2,704 | 2,774 | -0.55% | 114 | 23.7 | Township |
| Butler township | 18 | 2,618 | 2,551 | 0.81% | 109 | 24.0 | Township |
| Clay township | 19 | 2,477 | 2,543 | -0.4% | 99 | 25.1 | Township |
| Muddy Creek township | 20 | 2,157 | 2,206 | -0.6% | 95 | 22.6 | Township |
| Evans City | 21 | 1,672 | 1,740 | -1.01% | 2,044 | 0.8 | Borough |
| Mars | 22 | 1,412 | 1,462 | -0.91% | 3,004 | 0.5 | Borough |
| Saxonburg | 23 | 1,372 | 1,428 | -1.01% | 1,514 | 0.9 | Borough |
| Worth township | 24 | 1,360 | 1,397 | -0.44% | 54 | 25.0 | Township |
| Brady township | 25 | 1,198 | 1,215 | 0.17% | 71 | 17.0 | Township |
| Prospect | 26 | 1,081 | 1,120 | -0.92% | 265 | 4.1 | Borough |
| Cherry township | 27 | 1,045 | 1,053 | 0.1% | 41 | 25.6 | Township |
| Harmony | 28 | 918 | 950 | -0.86% | 2,330 | 0.4 | Borough |
| Chicora | 29 | 884 | 918 | -1.01% | 1,659 | 0.5 | Borough |
| Harrisville | 30 | 793 | 820 | -0.88% | 986 | 0.8 | Borough |
| Connoquenessing | 31 | 782 | 673 | 3.58% | 577 | 1.4 | Borough |
| Valencia | 32 | 740 | 539 | 7.25% | 2,176 | 0.3 | Borough |
| East Butler | 33 | 736 | 764 | -0.94% | 706 | 1.0 | Borough |
| Bruin | 34 | 403 | 422 | -1.23% | 221 | 1.8 | Borough |
| Callery | 35 | 345 | 359 | -1.15% | 642 | 0.5 | Borough |
| West Liberty | 36 | 319 | 333 | -1.24% | 83 | 3.8 | Borough |
| Eau Claire | 37 | 296 | 308 | -1% | 232 | 1.3 | Borough |
| Portersville | 38 | 221 | 231 | -1.34% | 278 | 0.8 | Borough |
| Barkeyville | 39 | 183 | 190 | -1.08% | 55 | 3.3 | Borough |
| West Sunbury | 40 | 175 | 182 | -1.13% | 1,591 | 0.1 | Borough |
| Petrolia | 41 | 171 | 178 | -1.16% | 433 | 0.4 | Borough |
| Karns City | 42 | 165 | 172 | -1.2% | 455 | 0.4 | Borough |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Butler township is the largest city in Butler County.
Karns City is the smallest city in Butler County.
There are 42 cities in Butler County, Pennsylvania.