Area Code Lookup
What Area Code Is Diamond Bar?
2 area codes serve Diamond Bar · California
Diamond Bar is served by area codes 840, 909. It is located in California.
Area Codes Serving Diamond Bar
Frequently Asked Questions
What area code is Diamond Bar?
Diamond Bar is served by area codes 840, 909. It is located in California.
Why does Diamond Bar have multiple area codes?
As demand for phone numbers increased, NANPA added area codes through splits (dividing the region) or overlays (layering a new code over the same geography). Diamond Bar now has 2 area codes — 840 and 909 — covering the same or overlapping areas.
How do I call Diamond Bar from outside the US?
To call Diamond Bar from abroad, dial +1 followed by the area code and 7-digit local number (e.g. +1-840-XXX-XXXX). The +1 is the country code for all NANPA countries.