The Walla Walla city flag was adopted by the City Council in July 2021 after a two-phase design contest that invited members of the public to submit original designs and participate in the selection process. It was designed by Lindsay Tebeck of Walla Walla, who describes its symbolism as: 

The lines prominent in this design are representative of Walla Walla's notorious rolling hills, blue mountains, and many streams. The drastic yellow circle, whose color comes from the Washington state flag's emblem, symbolizes the rising sun. It both adds body to the hills by peaking over them and casting a reflection in interpretative waters below. The green in the hills and blue in the sky are also pulled straight from the Washington state flag.

This flag replaced the original city flag, which was designed in 2008 by Council member Jerry Cummins and Executive Assistant to the City Manager Carol Pritcher.