19 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Waterbury | 1 | 116,917 | 113,889 | 0.43% | 4,094 | 29 | City |
| Bristol | 2 | 62,920 | 60,744 | 0.58% | 2,383 | 26 | City |
| Shelton | 3 | 43,826 | 40,762 | 1.18% | 1,431 | 31 | City |
| Cheshire | 4 | 33,380 | 28,310 | 4.33% | 1,017 | 33 | Township |
| Naugatuck | 5 | 32,427 | 31,494 | 0.48% | 1,979 | 16 | Borough |
| Watertown | 6 | 22,787 | 22,085 | 0.64% | 785 | 29 | Township |
| Southbury | 7 | 20,624 | 19,863 | 0.69% | 529 | 39 | Township |
| Ansonia | 8 | 19,344 | 18,896 | 0.39% | 3,214 | 6 | City |
| Seymour | 9 | 17,389 | 16,711 | 0.72% | 1,198 | 15 | Township |
| Wolcott | 10 | 16,739 | 16,131 | 0.69% | 821 | 20 | Township |
| Oxford | 11 | 13,444 | 12,711 | 0.67% | 411 | 33 | Township |
| Derby | 12 | 13,216 | 12,312 | 1.16% | 2,614 | 5 | City |
| Plymouth | 13 | 12,011 | 11,652 | 0.55% | 549 | 22 | Township |
| Woodbury | 14 | 10,094 | 9,712 | 0.67% | 278 | 36 | Township |
| Prospect | 15 | 9,685 | 9,374 | 0.58% | 682 | 14 | Township |
| Middlebury | 16 | 8,157 | 7,573 | 0.82% | 459 | 18 | Township |
| Thomaston | 17 | 7,634 | 7,439 | 0.45% | 637 | 12 | Township |
| Beacon Falls | 18 | 6,375 | 6,008 | 0.82% | 659 | 10 | Township |
| Bethlehem | 19 | 3,477 | 3,389 | 0.4% | 179 | 19 | Township |
Waterbury is the largest city in Naugatuck Valley Planning Region, with a population of 116,917.
Bethlehem is the smallest city in Naugatuck Valley Planning Region, with a population of 3,477.
There are 19 cities in Naugatuck Valley Planning Region, Connecticut.