He graduated from Baldwin High School in 2003, Georgia College & State University in 2006, and the Walter F. Georgia School of Law in 2009, where he was a member of the Mercer Law Review and Journal of Southern Legal History. McMullen practiced law in Macon for five years before returning to Milledgeville in 2015. He is active in the community as the Worship Committee Chairman for First United Methodist Church, Secretary for the Milledgeville Jaycees, Senior Steward of Benevolent Lodge #3 F&AM, Trustee of Lockerly Arboretum and board member of the Old Capital Museum Society. McMullen lives with his wife, Ruth, and sons Jack and George in Milledgeville.