Mitchell County is in the prairie of west central Texas, bound on the east by Nolan County, on the south by Sterling and Coke counties, on the west by Howard County, and on the north by Scurry County.

The county center is at 32°18' north latitude and 100°55' west longitude. Colorado City, the largest town, is in the northeastern part of the county, roughly 229 miles west of Fort Worth.

The area was named for Asa and Eli Mitchell, prominent participants in the Texas Revolution. The county encompasses 912 square miles of prairieland surfaced mainly with sandy, red, and dark soils.