Sedalia is an unincorporated community and census-designated place (CDP) in Douglas County, Colorado, United States. The CDP population was 206 at the 2010 census. The Sedalia Post Office has the ZIP code 80135.
Sedalia is located in northwestern Douglas County at 39°26′16″N 104°57′51″W (39.437892, −104.964117), along U.S. Route 85, which leads 8 miles (13 km) southeast to Castle Rock, the county seat, and north 24 miles (39 km) to downtown Denver.
According to the United States Census Bureau, the Sedalia CDP has a total area of 1.4 square miles (3.5 km2), all of it land. Sedalia is in the valley of Plum Creek, a north-flowing tributary of the South Platte River.