| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Sturgis | 1 | 10,866 | 11,121 | -0.31% | 1,599 | 7 | City |
| Three Rivers | 2 | 7,904 | 7,972 | -0.08% | 1,414 | 6 | City |
| Constantine | 3 | 4,031 | 4,051 | -0.3% | 117 | 34 | Township |
| White Pigeon | 4 | 3,992 | 3,762 | 2.54% | 159 | 25 | Township |
| Nottawa | 5 | 3,865 | 3,688 | 1.5% | 109 | 36 | Township |
| Lockport | 6 | 3,852 | 3,730 | 0.71% | 135 | 28 | Township |
| Sherman | 7 | 3,455 | 3,448 | -0.2% | 105 | 33 | Township |
| Fabius | 8 | 3,327 | 3,312 | 0.06% | 104 | 32 | Township |
| Colon | 9 | 3,321 | 3,331 | -0.45% | 97 | 34 | Township |
| Burr Oak | 10 | 2,624 | 2,629 | -0.42% | 74 | 35 | Township |
| Mendon | 11 | 2,549 | 2,575 | -0.62% | 73 | 35 | Township |
| Park | 12 | 2,363 | 2,391 | -0.46% | 68 | 35 | Township |
| Nottawa | 13 | 2,220 | 2,183 | -0.22% | 63 | 35 | Township |
| Sturgis | 14 | 2,012 | 2,048 | -0.49% | 115 | 17 | Township |
| Constantine | 15 | 1,983 | 1,987 | 0% | 1,212 | 2 | Village |
| White Pigeon | 16 | 1,822 | 1,726 | -0.11% | 1,293 | 1 | Village |
| Flowerfield | 17 | 1,597 | 1,596 | -0.62% | 45 | 35 | Township |
| Fawn River | 18 | 1,523 | 1,525 | -0.26% | 80 | 19 | Township |
| Mottville | 19 | 1,428 | 1,438 | -0.56% | 74 | 19 | Township |
| Centreville | 20 | 1,374 | 1,309 | 0% | 928 | 1 | Village |
| Colon | 21 | 1,178 | 1,209 | -0.34% | 857 | 1 | Village |
| Leonidas | 22 | 1,155 | 1,156 | -0.26% | 33 | 36 | Township |
| Florence | 23 | 1,138 | 1,150 | -0.35% | 34 | 33 | Township |
| Mendon | 24 | 857 | 886 | -0.58% | 876 | 1 | Village |
| Burr Oak | 25 | 751 | 772 | -0.53% | 747 | 1 | Village |
Sturgis is the largest city in St. Joseph County, with a population of 10,866.
Burr Oak is the smallest city in St. Joseph County, with a population of 751.
There are 25 cities in St. Joseph County, Michigan.