Mann is the son of Robert Mann, Sr. (1924-2008), a native of Beaumont, Texas, and the former Charlene Elizabeth Wellhausen (born c. 1934). The senior Mann died in Fredericksburg, Virginia, the place of residence of their son, Paul Edward Mann. Bob Mann, who was also born in Beaumont, has a sister, Sarah Elizabeth Luker of Seabrook, near Houston, Texas. The senior Mann was a veteran of the United States Coast Guard during World War II and was employed by Sun Oil Company and was for more than two decades a Church of Christ minister in Texas, Louisiana, and New Mexico.
Mann is married to the former Cynthia Ann "Cindy" Horaist (born June 1961), the executive director of the Louisiana Prison Chapel Foundation, which in 2013 sponsored the drama, The Life of Jesus Christ, performed by inmates at the Louisiana State Penitentiary in Angola. The couple has two children.
Mann attended the University of Louisiana at Monroe, where Dave Norris was his economics professor; since 1978, Norris has been the mayor of West Monroe. Mann worked for the Monroe News-Star, where he was assigned to cover the West Monroe City Hall. He left in 1983 to work as political writer for the since-defunct Shreveport Journal in Shreveport, Louisiana. Mann received his graduate degree from California State University, Dominguez Hills.
An active Democrat, Mann joined the staff of U.S. Senator Russell B. Long of Louisiana late in Long's lengthy tenure in office. He continued as press secretary (and later as state director) under Long's successor, John Breaux, another Democrat. In 1990, he was press secretary for the final reelection of U.S. Senator J. Bennett Johnston, Jr., who defeated the former Ku Klux Klansman David Duke, then a member of the Louisiana House of Representatives. In 2003, Mann was communications director for Kathleen Babineaux Blanco, the Lafayette Democrat and lieutenant governor who defeated Republican Bobby Jindal for governor of Louisiana but bowed out after one term, only to be succeeded in 2008 by Jindal.
Mann continued to work in the Blanco administration until 2006, when he joined LSU, from which forum he writes and speaks extensively on political topics. In addition to the Manship Chair, he was from 2011 to 2013 the director of the LSU Reilly Center for Media and Public Affairs. At the centennial observance of the LSU School of Journalism, Mann reflected on the heritage of his institution: "We've gone from being a journalism school, to being a multi-dimensional mass communication school, to being all that, plus finding a way to teach practical politics to our students. I believe we are unique in that regard, and it really gives us a leg up in recruiting.”
Mann's often-cited blog is called "Something Like the Truth: Robert Mann on Politics, Louisiana, and Life". He is highly critical of the Jindal administration, having in 2013 criticized the governor's position on health care and education. He also scolds Louisiana's Republican U.S. Senator David Vitter.
One of Mann's recent books, Daisy Petals and Mushroom Clouds: LBJ, Barry Goldwater and the Ad that Changed American Politics, which according to The Washington Post, is one of the best political books of 2011. His other books include:A Journalist’s Diplomatic Mission: Ray Stannard Baker’s World War I Diary, edited with John Maxwell Hamilton, Louisiana State University Press, 2012
Political Communication: The Manship School Guide, edited with David Perlmutter, LSU Press, 2011
Wartime Dissent in America: A History and Anthology, Palgrave Macmillan, 2010
When Freedom Would Triumph: The Civil Rights Struggle in Congress, 1954-1968, LSU Press, 2007
A Grand Delusion: America's Descent into Vietnam, Basic Books, 2001
The Walls of Jericho: Lyndon Johnson, Hubert Humphrey, Richard Russell and the Struggle for Civil Rights, Harcourt Brace, 1996
The Complete Idiot’s Guide to the Cold War, Alpha Books, 2002
Legacy to Power: Senator Russell Long of Louisiana, Paragon House, 1992.
In February 2014, Mann, along with several other political figures, including John S. Hunt, III, a cousin of Senator Russell Long, and Senator Long's mother, Rose McConnell Long, were inducted into the Louisiana Political Museum and Hall of Fame in Winnfield.