The No. 1 firm's pitch focused on tastiness, health benefits and the many ways walnuts fit into a family's menu.
In announcing the selection, Dennis Ballint, executive director of the Board, highlighted Edelman's strong network, creativity and ability to raise the awareness of walnuts nationally.
The Walnut Marketing Board, which was established in 1948, added California to its name in 2008 to provide origin destination information.
Torme Lauricella currently handles the work.