Diamond Bar, California Area Code
Diamond Bar, CA is officially utilizing an area code overlay in which area codes 909 and 840 serve the same geographic area. Ten digit dialing (area code + seven digit number) is necessary.
In addition to Diamond Bar, CA area code information read more about area code 909 and 840 details and California area codes.
Diamond Bar, CA is located in Los Angeles County and observes the Pacific Time Zone. View our Times by Area Code tool.