Wylie is a city and northeastern suburb of Dallas, that was once solely located in Collin County, but now extends into neighboring Dallas an…Wylie is a city and northeastern suburb of Dallas, that was once solely located in Collin County, but now extends into neighboring Dallas and Rockwall counties in the U.S. state of Texas. It is located on State Route 78 about 24 miles northeast of central Dallas and centrally located between nearby Lavon Lake and Lake Ray Hubbard.