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 are W. 120th Ave. on the north, Sheridan Blvd. 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 portion of southeast of Arvada is located in Adams County, Colorado.