There are 23 zip codes in Middlesex County, Connecticut. The most populated is 6457, located in Middletown. * 2024 populations estimated based on the latest ACS 5-year data.

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Zip Code
Population
City
645747,030Middletown
641614,250Cromwell
641313,271Clinton
642412,372East Hampton
647510,492Old Saybrook
64809,409Portland
64227,197Durham
64986,829Westbrook
64196,216Killingworth
64415,234Higganum
64234,887East Haddam
64174,445Deep River
64123,740Chester
64693,377Moodus
64263,377Essex
64383,079Haddam
64552,834Middlefield
64422,514Ivoryton
64811,406Rockfall
64591,122Middletown
6409863Centerbrook
6414334Cobalt
6456271Middle Haddam
showing: 23 rows

Zip Codes in Middlesex County, Connecticut by Population (2024)