Harris has spent her entire professional life in the trenches as a courtroom prosecutor. After graduating from U.C. Hastings College of the Law, she took a position in the Alameda County District Attorney's Office, where she specialized in prosecuting child sexual assault cases. As a Deputy District Attorney she also prosecuted cases for homicide and robbery. She worked at that office from 1990 to 1998 before going on to serve in the San Francisco District Attorney’s Office.
In 1998, Harris was named managing attorney of the Career Criminal Unit of the San Francisco District Attorney’s Office, where she prosecuted three strikes cases and serial felony offenders. She then served as the head of the San Francisco City Attorney’s Division on Families and Children.
In 2004-2010, Kamala Harris served as the first woman District Attorney in San Francisco's history, and as the first African American woman and South Asian American woman in California to hold the office.