Route 28 begins as six lanes at VA 7 in Sterling in a complete interchange. It is known as Sully Road through this stretch, although it is sub-designated Darrell Green Boulevard, after Washington Redskins player #28, Darrell Green. Heading south, Route 28 passes the Dulles Town Center shopping mall and through the industrial and commercial areas of Dulles, passing shopping centers and stores such as Wegmans, Carmax, Wal-Mart, and Best Buy.

The next interchange is Route 625, Waxpool Road and Church Road, which lead into Ashburn and Sterling, respectively. The America Online corporate headquarters are next to the highway. Continuing south through Loudoun County, Route 28 follows the southern edge of Sterling. The final interchange in Loudoun County is State Route 267 near Dulles International Airport.