Home to Harvard University and MIT, Cambridge sits just across the Charles River from Boston and is one of the world’s great centers of learning and biotech innovation. As part of the Greater Boston core, it shares the 617 code and its overlay. This guide breaks down Cambridge’s 617 and 857 codes, the required 10-digit dialing, major ZIP codes, and local scam warnings.
Cambridge Area Codes at a Glance
| Detail | Information |
|---|---|
| Primary Area Code(s) | 617 |
| Overlay Area Code(s) | 857 |
| Time Zone | Eastern Time (ET) – EST / EDT |
| Major County | Middlesex County |
| Region | Greater Boston |
| Dialing Format | 10-digit dialing required |
Area Code Breakdown & Regional Mapping
617 – Boston’s Core Code
Area code 617 is Boston’s original 1947 code, and it covers Cambridge as part of the inner Greater Boston core. A 617 number ties Cambridge directly into the region’s prestigious central dialing area.
857 – Greater Boston Overlay
Area code 857 is the 2001 overlay for the 617 region, sharing the same Greater Boston geography that includes Cambridge. Many newer Cambridge lines carry an 857 prefix, fully local to existing 617 numbers.
Neighborhoods & Local Coverage
Cambridge’s 617/857 codes cover a compact “City of Squares.” Harvard Square anchors the historic west end around Harvard University, while Kendall Square to the east has become one of the densest biotech and technology hubs on earth, packed with labs and startups near the MIT campus.
Between them, the same codes reach the lively Central Square arts district, the residential Porter Square and Inman Square neighborhoods, and the East Cambridge and Cambridgeport areas along the river. As part of the Greater Boston core, Cambridge shares the 617/857 codes with Boston and Somerville next door.
Local Dialing Rules & International Format
Cambridge and all of eastern Massachusetts have required 10-digit dialing for years — always dial the area code plus the 7-digit number. The Greater Boston core uses 617, overlaid by 857. Across the river, Boston shares the same codes.
To call Cambridge from outside the United States, dial your country’s exit code, then the U.S. country code +1, followed by the 10-digit number (for example, +1 617 XXX-XXXX). From inside the U.S. and Canada, simply dial 1 before the 10-digit number for long-distance calls.
Major ZIP Codes Covered
The 617 service area spans many of Cambridge’s core ZIP codes, including 02138, 02139, 02140, 02141, and 02142.
Spam & Scam Call Warnings in Cambridge
Cambridge residents report neighbor-spoofing robocalls faking a local 617 prefix, plus student-targeted tuition and rental-deposit scams around Harvard and MIT. Fake utility-shutoff and package-delivery scams are also common.
| Scam Type | What to Watch For |
|---|---|
| Neighbor Spoofing | Calls that mimic a local 617 prefix to look familiar. |
| Utility / Toll Scams | Threats to shut off power or demand toll payment via gift cards. |
| IRS / Government | Robocalls claiming legal action — agencies never call to demand instant payment. |
Red flag: Any caller who pressures you to pay immediately with gift cards, wire transfers, or cryptocurrency is almost certainly running a scam. Hang up and verify through an official number.
↑ See the complete list of All US Area Codes by State for every code across the country.
Nearby & Related Massachusetts Cities
Frequently Asked Questions
What area code is Cambridge, MA?
Cambridge uses area code 617, shared with Boston, overlaid by 857.
Does Cambridge have the same area code as Boston?
Yes. As part of the Greater Boston core, Cambridge shares the 617/857 codes with Boston.
Do I need to dial 10 digits in Cambridge?
Yes. All local calls in Cambridge and Greater Boston require 10-digit dialing.
What time zone is Cambridge in?
Cambridge observes Eastern Time (EST/EDT), like all of Massachusetts.
Is 857 a real Cambridge area code?
Yes. 857 is the FCC-approved overlay for the 617 region, which includes Cambridge as part of the Greater Boston core. New local lines may be assigned an 857 number alongside 617.
Stay Safe & Explore More
- Verify an unknown caller in our Scam Alerts directory.
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