ZIP codes in Middlesex County

111 ZIPs touch Middlesex County, Massachusetts. The blue dashed line is the county border; orange ZIPs reach into it.

111

ZIP codes

cross the county line

1,653,842

people in these ZIPs

counties in MA

Most people

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Middlesex County ZIP list

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Questions people actually ask

How many ZIP codes are in Middlesex County, Massachusetts?

111 ZIP codes reach into Middlesex County, including 28 PO Box or single-address ZIPs placed by the town they serve. 5 of them are only partly in the county and also cover a neighboring county.

Which ZIP code in Middlesex County has the most people?

02148 (Malden) has about 65,906 residents, the most of any ZIP touching Middlesex County, in the Census Bureau’s ACS 2020–2024 estimates.

Can a ZIP code be in Middlesex County and another county?

Yes. ZIP codes follow mail routes, not county lines. Rows marked with a percentage show how much of that ZIP’s land is in Middlesex County. For one address, pin the exact spot on the ZIP finder to see its county.

Where does this list come from?

ZIP areas and their county overlaps come from the Census Bureau’s 2020 ZIP Code Tabulation Area to county relationship file. PO Box ZIPs have no area, so each is placed in the county of the ZIP area nearest the town it serves.

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Updated 2026-11-10 · Where the data comes from