| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Slidell | 1 | 28,306 | 28,606 | -0.12% | 1,853 | 15 | City |
| Mandeville | 2 | 12,958 | 12,822 | 0.31% | 1,385 | 9 | City |
| Covington | 3 | 11,754 | 11,578 | 0.28% | 1,466 | 8 | City |
| Abita Springs | 4 | 2,784 | 2,622 | 1.13% | 603 | 5 | Town |
| Pearl River | 5 | 2,743 | 2,555 | 1.03% | 735 | 4 | Town |
| Madisonville | 6 | 884 | 848 | 0.8% | 350 | 3 | Town |
| Folsom | 7 | 859 | 775 | 1.54% | 432 | 2 | Village |
| Sun | 8 | 402 | 395 | 0.25% | 94 | 4 | Village |
Slidell is the largest city in St. Tammany Parish, with a population of 28,306.
Sun is the smallest city in St. Tammany Parish, with a population of 402.
There are 8 cities in St. Tammany Parish, Louisiana.