25 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Iowa Falls | 1 | 4,968 | 5,105 | -0.5% | 922 | 5 | City |
| Iowa Falls | 2 | 4,968 | 5,090 | -0.5% | 922 | 5 | City |
| Eldora | 3 | 2,581 | 2,659 | -0.54% | 603 | 4 | City |
| Eldora | 4 | 2,581 | 2,650 | -0.54% | 603 | 4 | City |
| Ackley | 5 | 1,524 | 1,598 | -0.91% | 620 | 2 | City |
| Ackley | 6 | 1,524 | 1,594 | -0.91% | 620 | 2 | City |
| Hubbard | 7 | 831 | 861 | -0.72% | 468 | 2 | City |
| Hubbard | 8 | 831 | 859 | -0.72% | 468 | 2 | City |
| Alden | 9 | 732 | 763 | -0.81% | 475 | 2 | City |
| Alden | 10 | 732 | 761 | -0.81% | 475 | 2 | City |
| Radcliffe | 11 | 536 | 556 | -0.74% | 538 | 1 | City |
| Radcliffe | 12 | 536 | 554 | -0.74% | 538 | 1 | City |
| Union | 13 | 374 | 392 | -1.06% | 655 | 1 | City |
| Union | 14 | 374 | 391 | -1.06% | 655 | 1 | City |
| McCallsburg | 15 | 357 | 350 | 0.28% | 783 | 0 | City |
| McCallsburg | 16 | 357 | 350 | 0.28% | 783 | 0 | City |
| Steamboat Rock | 17 | 260 | 266 | -0.38% | 481 | 1 | City |
| Steamboat Rock | 18 | 260 | 265 | -0.38% | 481 | 1 | City |
| New Providence | 19 | 232 | 237 | -0.43% | 232 | 1 | City |
| New Providence | 20 | 232 | 236 | -0.43% | 232 | 1 | City |
| Garden City | 21 | 159 | 150 | 7.43% | 159 | 1 | CDP |
| Whitten | 22 | 97 | 100 | -1.02% | 195 | 0 | City |
| Whitten | 23 | 97 | 100 | -1.02% | 195 | 0 | City |
| Buckeye | 24 | 81 | 84 | -1.22% | 82 | 1 | City |
| Buckeye | 25 | 81 | 84 | -1.22% | 82 | 1 | City |
Iowa Falls is the largest city in Hardin County, with a population of 4,968.
Buckeye is the smallest city in Hardin County, with a population of 81.
There are 25 cities in Hardin County, Iowa.