COUNTY · NJ
Middlesex County, New Jersey
Middlesex County is a county in New Jersey with FIPS code 34023 and an estimated population of 863,623 (Census 2023), 2nd largest of 21 in the state.
County facts
- Name
- Middlesex County
- State
- New Jersey
- Type
- county
- FIPS code
- 34023
- State FIPS
- 34
- Population (2023)
- 863,623
- Change since 2020
- +0.3%
- State rank
- 2 of 21
Population is the Census Bureau’s Vintage 2023 estimate.
Other counties in New Jersey
Questions
What is the FIPS code for Middlesex County?
Middlesex County, New Jersey has the five-digit FIPS code 34023: 34 for the state and 023 for the county.
What state is Middlesex County in?
Middlesex County is in New Jersey.
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.