Ransone was raised in Baltimore, Maryland, the son of Joyce (Peterson) and James Finley Ransone II. A former musician, at the age of twenty-seven Ransone had developed a heroin habit and a debt of $30,000, but radically altered his lifestyle in moving to Namibia for eight months, undergoing immersion into his role as Person in Generation Kill. He appears in a small recurring role in the HBO series Treme. In 2011, Ransone and Michael Zegen were cast in recurring roles in the HBO comedy series How to Make It in America. Ransone appeared in the show's pilot episode and a further six episodes after that.
In 2006, Ransone saved his neighbor from being raped, by answering her cries for help, and fighting off her alleged assailant.
He was interviewed in the film Freakonomics as a bystander regarding the issue of ethnicity and names.