Terry J. Flanagan graduated from St Louis University School of Law in 1970, obtaining his Juris Doctorate. He obtained his undergraduate degree from St Louis University in 1967. He is a member of the Missouri Bar and licensed to practice before the Missouri Court of Appeals for the Eastern District of Missouri, as well as the Supreme Court of the State of Missouri. He is also a regular practitioner before the United States District Court for the Eastern District of Missouri, as well as other federal district courts within the state.

He has appeared in both state and federal courts and has defended individuals in various jurisdictions other than the State of Missouri, including Illinois, Massachusetts, Florida, New Mexico, Texas, Arkansas, California, Ohio, Kentucky, Colorado and Indiana. He has also successfully undertaken appeals to the Missouri Court of Appeals, as well as the Supreme Court of the State of Missouri. Other areas of practice in which Mr. Flanagan has represented individuals include family law and personal injury.