18 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| South Bend | 1 | 103,803 | 103,350 | 0.09% | 2,478 | 42 | City |
| Penn | 2 | 68,714 | 68,598 | 0.03% | 1,097 | 63 | Township |
| Mishawaka | 3 | 51,013 | 51,047 | -0.01% | 2,800 | 18 | City |
| Clay | 4 | 34,386 | 34,171 | 0.07% | 1,737 | 20 | Township |
| Harris | 5 | 24,685 | 24,478 | 0.11% | 1,175 | 21 | Township |
| Centre | 6 | 14,519 | 14,395 | 0.1% | 751 | 19 | Township |
| German | 7 | 10,084 | 9,992 | 0.1% | 600 | 17 | Township |
| Olive | 8 | 4,380 | 4,348 | -0.02% | 76 | 57 | Township |
| Union | 9 | 3,493 | 3,476 | 0.03% | 81 | 43 | Township |
| Greene | 10 | 2,967 | 2,947 | 0.1% | 86 | 34 | Township |
| Lincoln | 11 | 2,873 | 2,868 | -0.07% | 129 | 22 | Township |
| Osceola | 12 | 2,604 | 2,584 | 0.15% | 1,929 | 1 | Town |
| Walkerton | 13 | 2,099 | 2,093 | 0.05% | 1,104 | 2 | Town |
| New Carlisle | 14 | 1,918 | 1,891 | 0.26% | 945 | 2 | Town |
| North Liberty | 15 | 1,633 | 1,626 | 0.06% | 1,589 | 1 | Town |
| Lakeville | 16 | 879 | 874 | 0.11% | 1,404 | 1 | Town |
| Roseland | 17 | 853 | 851 | 0% | 2,263 | 0 | Town |
| Indian Village | 18 | 114 | 116 | -0.87% | 1,267 | 0 | Town |
South Bend is the largest city in St. Joseph County, with a population of 103,803.
Indian Village is the smallest city in St. Joseph County, with a population of 114.
There are 18 cities in St. Joseph County, Indiana.