| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Ionia | 1 | 11,928 | 13,353 | -2.29% | 2,204 | 5 | City |
| Boston | 2 | 6,150 | 6,033 | 0.47% | 175 | 35 | Township |
| Belding | 3 | 6,008 | 5,947 | 0.13% | 1,272 | 5 | City |
| Ionia | 4 | 4,157 | 3,995 | 0.78% | 124 | 33 | Township |
| Portland | 5 | 4,006 | 3,897 | 0.65% | 124 | 32 | Township |
| Odessa | 6 | 3,985 | 3,920 | 0.48% | 112 | 36 | Township |
| Portland | 7 | 3,761 | 3,806 | -0.24% | 1,431 | 3 | City |
| Lyons | 8 | 3,598 | 3,523 | 0.5% | 100 | 36 | Township |
| Easton | 9 | 3,156 | 3,067 | 0.64% | 111 | 28 | Township |
| Danby | 10 | 3,011 | 2,953 | 0.47% | 86 | 35 | Township |
| Orleans | 11 | 2,781 | 2,671 | 0.83% | 79 | 35 | Township |
| Campbell | 12 | 2,453 | 2,403 | 0.53% | 69 | 36 | Township |
| Otisco | 13 | 2,316 | 2,273 | 0.56% | 75 | 31 | Township |
| Berlin | 14 | 2,170 | 2,132 | 0.46% | 52 | 41 | Township |
| Lake Odessa | 15 | 2,094 | 2,052 | 0.24% | 2,353 | 1 | Village |
| Ronald | 16 | 1,911 | 1,854 | 0.63% | 53 | 36 | Township |
| Keene | 17 | 1,756 | 1,726 | 0.4% | 49 | 36 | Township |
| Saranac | 18 | 1,387 | 1,373 | 0.07% | 1,206 | 1 | Village |
| North Plains | 19 | 1,206 | 1,185 | 0.5% | 34 | 36 | Township |
| Sebewa | 20 | 1,153 | 1,130 | 0.52% | 32 | 36 | Township |
| Orange | 21 | 1,024 | 1,003 | 0.59% | 28 | 36 | Township |
| Lyons | 22 | 782 | 771 | 0.26% | 643 | 1 | Village |
| Muir | 23 | 651 | 645 | 0% | 914 | 1 | Village |
| Pewamo | 24 | 517 | 512 | 0% | 517 | 1 | Village |
| Clarksville | 25 | 409 | 404 | 0% | 812 | 1 | Village |
| Hubbardston | 26 | 342 | 339 | 0% | 235 | 1 | Village |
Ionia is the largest city in Ionia County, with a population of 11,928.
Hubbardston is the smallest city in Ionia County, with a population of 342.
There are 26 cities in Ionia County, Michigan.