Darrell Castle grew up in East Tennessee in a small town outside of Kingsport. He graduated from Ketron High School in 1966 and attended East Tennessee State University (ETSU), where he received a Bachelor of Science in History and a Bachelor of Science in Political Science in 1970.

Darrell was commissioned as an officer in The United States Marine Corp in 1970, where he served four years. After leaving the Marines, he went to graduate school in history at ETSU and then entered Memphis State University Law School (currently known as the University of Memphis) where he graduated with a Juris Doctorate in 1979.

In 1984, Darrell opened a private firm that later grew into Darrell Castle & Associates. He has started law firms in Milwaukee, WI, Detroit, MI, St. Louis, MO, and Kansas City, MO. Darrell has 30 years legal experience and currently concentrates in the areas of consumer bankruptcy and personal injury.