Arvada is located primarily in Jefferson County, Colorado. Jefferson County is the largest county in Colorado with a population estimated at 535,000. General boundaries for the county include West 120th Avenue in Westminster on the north, Sheridan Boulevard on the east, and Pike National Forest to the south. The county extends west into the mountains to meet Gilpin, Clear Creek and Park counties.
A small section of Arvada, in the southeast section, is located in Adams County, Colorado.