Margo Martindale was born in Jacksonville, Texas, to Margaret (Pruitt) and William Everett Martindale, a lumber company owner and dog handler. She is the youngest of three children and the only daughter. Margo attended Lon Marris College, later transferred to University of Michigan at Ann Arbor, and did a summer study at Harvard University. She made her film debut appearance in Days of Thunder (1990), in which she played the minor role of Donna. Notable roles include Sister Colleen, Susan Sarandon's fellow nun in Dead Man Walking (1995), and a brief but memorable role as the selfish mother of Hilary Swank's character in Million Dollar Baby (2004).