Area code 925

Numbering plan areas in California (blue) and border states. Area code 925 is shown in red.

Area code 925 is a California telephone area code that was split from area code 510 on March 14, 1998. It covers the inland portions of the East Bay counties of Alameda and Contra Costa in the northern area of California.

The area was originally part of area code 415, one of the first three area codes created in California in 1947, which originally covered all of central California. In 1991, area code 510 was created to encompass most of the East Bay. Area code 925 was created March 14, 1998, when area code 510 was split along the natural border of the Berkeley Hills.

The area code includes southeastern Alameda County (Dublin, Pleasanton, Livermore, Sunol, and unincorporated areas surrounding those communities), and all of Contra Costa County except the western part (El Cerrito to Crockett).

Prior to October 2021, area code 925 had telephone numbers assigned for the central office code 988. In 2020, 988 was designated nationwide as a dialing code for the National Suicide Prevention Lifeline, which created a conflict for exchanges that permit seven-digit dialing. This area code was therefore scheduled to transition to ten-digit dialing by October 24, 2021.^[1]