| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Cambridge | 1 | 123,339 | 116,202 | 0.61% | 19,281 | 6 | City |
| Lowell | 2 | 119,847 | 115,783 | -0.1% | 8,806 | 14 | City |
| Newton | 3 | 91,483 | 88,806 | 0.82% | 5,131 | 18 | City |
| Somerville | 4 | 84,334 | 80,777 | 0.15% | 20,455 | 4 | City |
| Framingham | 5 | 72,952 | 72,090 | -0.09% | 2,913 | 25 | City |
| Malden | 6 | 66,362 | 66,047 | -0.01% | 13,154 | 5 | City |
| Waltham | 7 | 64,896 | 64,190 | -0.22% | 5,092 | 13 | City |
| Medford | 8 | 59,790 | 59,566 | -0.07% | 7,383 | 8 | City |
| Everett | 9 | 55,934 | 48,908 | 4.41% | 16,374 | 3 | City |
| Arlington | 10 | 46,426 | 46,164 | -0.29% | 9,029 | 5 | Town |
| Woburn | 11 | 44,112 | 40,792 | 0.34% | 3,487 | 13 | City |
| Marlborough | 12 | 43,391 | 41,635 | 1.45% | 2,080 | 21 | City |
| Billerica | 13 | 42,616 | 41,801 | -0.04% | 1,666 | 26 | Town |
| Chelmsford | 14 | 39,269 | 36,370 | 1.87% | 1,754 | 22 | Town |
| Natick | 15 | 36,919 | 36,894 | -0.14% | 2,468 | 15 | Town |
| Lexington | 16 | 34,694 | 34,367 | 0.13% | 2,111 | 16 | Town |
| Dracut | 17 | 32,858 | 32,492 | 0.23% | 1,589 | 21 | Town |
| Tewksbury | 18 | 32,166 | 31,085 | 0.83% | 1,552 | 21 | Town |
| Melrose | 19 | 29,527 | 29,710 | -0.24% | 6,305 | 5 | City |
| Wakefield | 20 | 29,473 | 27,076 | 0.82% | 3,986 | 7 | Town |
| Belmont | 21 | 27,013 | 27,210 | -0.39% | 5,813 | 5 | Town |
| Burlington | 22 | 26,762 | 26,001 | -0.06% | 2,278 | 12 | Town |
| Reading | 23 | 25,792 | 25,506 | -0.04% | 2,585 | 10 | Town |
| Acton | 24 | 25,114 | 23,950 | 1.32% | 1,264 | 20 | Town |
| Westford | 25 | 24,864 | 24,684 | 0.04% | 822 | 30 | Town |
| Stoneham | 26 | 24,189 | 23,146 | -0.26% | 4,021 | 6 | Town |
| Winchester | 27 | 23,676 | 22,901 | -0.14% | 3,925 | 6 | Town |
| Wilmington | 28 | 23,641 | 23,280 | 0.05% | 1,393 | 17 | Town |
| Hudson | 29 | 20,323 | 20,020 | -0.09% | 1,763 | 12 | Town |
| Hopkinton | 30 | 19,984 | 18,747 | 0.59% | 762 | 26 | Town |
| Sudbury | 31 | 19,619 | 18,863 | -0.12% | 808 | 24 | Town |
| Ashland | 32 | 19,115 | 18,822 | -0.32% | 1,549 | 12 | Town |
| Concord | 33 | 18,184 | 18,351 | -0.13% | 742 | 25 | Town |
| North Reading | 34 | 16,852 | 15,503 | 1.81% | 1,281 | 13 | Town |
| Holliston | 35 | 15,184 | 14,976 | -0.14% | 814 | 19 | Town |
| Bedford | 36 | 14,835 | 14,662 | -0.01% | 1,086 | 14 | Town |
| Wayland | 37 | 13,865 | 13,934 | -0.35% | 922 | 15 | Town |
| Tyngsborough | 38 | 12,760 | 12,388 | 0.31% | 760 | 17 | Town |
| Weston | 39 | 11,751 | 11,126 | 0.19% | 699 | 17 | Town |
| Pepperell | 40 | 11,745 | 11,559 | -0.14% | 520 | 23 | Town |
| Groton | 41 | 11,586 | 11,317 | 0.39% | 354 | 33 | Town |
| Maynard | 42 | 10,670 | 10,722 | -0.31% | 2,048 | 5 | Town |
| Littleton | 43 | 10,395 | 10,119 | -0.09% | 629 | 17 | Town |
| Ayer | 44 | 9,443 | 8,476 | 1.9% | 1,055 | 9 | Town |
| Townsend | 45 | 9,124 | 9,110 | -0.21% | 279 | 33 | Town |
| Shirley | 46 | 7,363 | 7,233 | 2.42% | 466 | 16 | Town |
| Stow | 47 | 7,225 | 7,145 | -0.32% | 417 | 17 | Town |
| Lincoln | 48 | 6,912 | 6,963 | -0.19% | 486 | 14 | Town |
| Boxborough | 49 | 5,492 | 5,491 | -0.29% | 534 | 10 | Town |
| Carlisle | 50 | 5,290 | 5,233 | 0.08% | 346 | 15 | Town |
| Sherborn | 51 | 4,456 | 4,390 | 0.02% | 282 | 16 | Town |
| Dunstable | 52 | 3,499 | 3,358 | 0.37% | 213 | 16 | Town |
| Ashby | 53 | 3,270 | 3,194 | -0.12% | 138 | 24 | Town |
Cambridge is the largest city in Middlesex County, with a population of 123,339.
Ashby is the smallest city in Middlesex County, with a population of 3,270.
There are 53 cities in Middlesex County, Massachusetts.