The County flag was designed by Ed Penniman, a Soquel resident. In describing the symbolism of the flag design, Mr. Penniman stated that the main symbol of the evergreen tree against a white background represents "reverence for nature and growth, upheld by a foundation of optimism and unity." The five bands in rainbow colors at the bottom of the flag represent the five county districts nonspecifically.

The flag was officially dedicated July 4, 1983.