Walnut Grove is a census-designated place (CDP) in Clark County, Washington, United States.

The community is bordered by the city of Vancouver to the southeast and west, and by the suburbs of Minnehaha to the south, Hazel Dell to the west, Salmon Creek to the northwest, Barberton to the north, and Five Corners to the east.

According to the United States Census Bureau, the Walnut Grove CDP has a total area of 3.8 square miles (9.9 km2), all of it land.

17.2% were of German, 10.8% English, 10.6% American, 10.0% Irish and 5.4% Norwegian ancestry according to Census 2000.

20.1% of all households were made up of individuals, and 6.2% had someone living alone who was 65 years of age or older.