Washington Township is one of eighteen townships in Buena Vista County, Iowa, United States.

As of the 2000 census, its population was 663.

Washington Township covers an area of 34.81 square miles (90.2 km2) and contains one incorporated settlement, Truesdale.

According to the USGS, it contains one cemetery, Buena Vista Memorial Park.

This article about the geography of Buena Vista County, Iowa is a stub.