Each of the five-member Board of Supervisors is elected for a four-year term to represent their district. By law, Supervisors are limited to three terms in office. The position of Chairperson rotates annually among the five members. Voters also elect the District Attorney, Sheriff, and Assessor in Santa Clara County. The Board convenes in regular session no more than once each week to set policy for County departments. It adopts ordinances that affect the unincorporated communities (areas outside of city jurisdictions), and oversees the budget. Santa Clara County operates under a "charter" form of government approved by voters in 1951 and most recently revised in November 1998.

The charter gives the County more responsibility and authority than is granted by the other two forms of state government. Under the charter, the Board appoints a County Executive to administer County government. The role of the County Executive includes recommending an annual budget to the Board as well as providing leadership on policy matters, directing a large and diverse workforce, and appointing many of the department heads. (Certain department heads are elected or are appointed directly by the Board of Supervisors.)