COUNTY · MA
Middlesex County, Massachusetts
Middlesex County is a county in Massachusetts with FIPS code 25017 and an estimated population of 1,623,952 (Census 2023), 1st largest of 14 in the state.
County facts
- Name
- Middlesex County
- State
- Massachusetts
- Type
- county
- FIPS code
- 25017
- State FIPS
- 25
- Population (2023)
- 1,623,952
- Change since 2020
- -0.3%
- State rank
- 1 of 14
Population is the Census Bureau’s Vintage 2023 estimate.
Other counties in Massachusetts
Questions
What is the FIPS code for Middlesex County?
Middlesex County, Massachusetts has the five-digit FIPS code 25017: 25 for the state and 017 for the county.
What state is Middlesex County in?
Middlesex County is in Massachusetts.
How do I know if an address is in this county?
Use the address lookup. ZIP codes and city names can cross county lines, so an address is the reliable check.
Sources: U.S. Census Bureau geographic reference files; Census Bureau Population Estimates, Vintage 2023. Last reviewed 2026-10-27.