Reviewed and updated October 9, 2026 by the SearchSystems.net editorial team. The arrest counts are the ones each agency reported to the FBI, as the FBI held them on October 8, 2026. The jail figures are from the Vera Institute of Justice's Incarceration Trends data. Every office link was opened and checked against the office's own site between September 23, 2026 and October 2, 2026.
Cambridge, Massachusetts, in Middlesex County, has about 121,000 residents (2024 Census Bureau estimate). A person kept in custody after an arrest in Cambridge is held at the county jail, run by the Middlesex Sheriff's Office, MA | Official Website, and the jail's record of each person held is a public record. This guide says where to look for someone in custody, what the jail holds and who books people into it.
This guide covers the search, the jail, who books people, state prison and common questions.
Related guides: Cambridge public records, Middlesex County inmate search, Cambridge arrest records, Cambridge warrants, Cambridge criminal records, Cambridge court records, Massachusetts arrest records and Massachusetts inmate search.
Finding Someone in Custody in Cambridge
A person kept in custody after an arrest in Cambridge is held at the county jail, run by the Middlesex Sheriff's Office, MA | Official Website, whichever agency made the arrest.
SearchSystems opened and checked the jail page of the Middlesex Sheriff's Office, MA | Official Website at middlesexsheriff.org (page title: Middlesex Sheriff's Office, MA), which answered when SearchSystems opened it on September 30, 2026.
That page is the office's jail information page rather than a roster.
The Middlesex County Jail by the Numbers
On an average day in 2025 the jail held about 710 people, down from about 790 in 2019. Its rated capacity in 2023, the last year with a capacity figure, was 1,464 beds, and it ran at 44 percent of it that year. The figures are from the Vera Institute of Justice's Incarceration Trends data.
Middlesex County has about 1.7 million residents (2024 Census Bureau estimate), so the jail holds about 4 people for every 10,000 residents.
Who Books People Into the Middlesex County Jail
The Middlesex Sheriff's Office, MA | Official Website and the agency that reports for Cambridge (filed by the FBI as Cambridge Police Department) make the arrests that end in a booking in and around Cambridge.
The FBI's agency list also places 12 campus police departments, one state agency and one state police unit in Middlesex County (the arrest records guide names each one).
The largest arrest counts reported to the FBI were Lowell's 3,961 for 2025, Cambridge's 1,872 for 2025 and Framingham's 1,049 for 2025.
Together, the 51 agencies in Middlesex County with all twelve months of 2025 on file reported 15,399 arrests to the FBI that year. Those kept in custody were booked into the county jail; a person cited and released at the scene was not.
The counts, agency by agency and year by year, are in Cambridge arrest records.
From the Jail to State Prison
The jail holds people awaiting trial and people serving short sentences. A person sentenced to prison in Middlesex County serves the sentence in a facility of the Massachusetts Department of Correction, whose inmate locator is at mass.gov/how-to/find-someone-housed-in-a-massachusetts-prison.
Frequently Asked Questions
How do I find an inmate in Cambridge?
Ask the Middlesex Sheriff's Office, MA | Official Website; its jail page SearchSystems verified is at middlesexsheriff.org.
How many people are in the Middlesex County jail?
About 710 on an average day in 2025, the latest year in the Vera Institute's jail data, against a rated capacity of 1,464 beds.
Where do people sentenced to prison in Middlesex County go?
To a facility of the Massachusetts Department of Correction; its inmate locator is at mass.gov.
Is this the official Cambridge website?
No. SearchSystems.net is an independent public records guide, online since 1997. It links to the official city, county, court and state offices described above and does not hold records, charge for them or take requests.