Martin-Green was born in Russellville, Alabama. She has one full sister and three older half-sisters. She had initially decided on becoming a psychologist before deciding to pursue a career in acting when she was in the tenth grade. After graduating from the University of Alabama in 2007 with a degree in theatre, she relocated to New York where she and her husband, Kenric, lived for five years before moving to California.
Martin-Green is married to Kenric Green. They met while acting in a play together in Princeton, New Jersey. Martin-Green gave birth to a boy named Kenric Justin Green II after his father on January 10, 2015, in Los Angeles. Martin-Green was pregnant during the filming of fifth season of The Walking Dead which she covered up using thick layers and using larger guns.