Lomax was born in Valdosta, Georgia. He attended Paine College in Augusta, Georgia, where he became editor of the student newspaper before he graduated in 1942. He pursued graduate studies at American University, where he was awarded an M.A. in 1944, and Yale University, where he earned a Ph.D. in 1947.

Lomax was married three times. His first wife was Betty Frank (1958—1961), his second was Wanda Kay (1961—1967), and his third was Robinette Kirk (1968—1970).

Lomax began his journalism career at the Afro-American and the Chicago Defender, two newspapers focused on news of interest to African-American readers. In 1958, he became the first Black television journalist when he joined WNTA-TV in New York.

In 1959, Lomax told his colleague Mike Wallace about the Nation of Islam. Lomax and Wallace produced a five-part documentary about the organization, The Hate That Hate Produced, which aired during the week of July 13, 1959. The program was the first time most white people heard about the Nation, its leader, Elijah Muhammad, and its charismatic spokesman, Malcolm X.

Lomax later became a freelance writer, and his articles were published in publications such as Harper's, Life Pageant, The Nation, and The New Leader. His subjects included the Civil Rights Movement, the Nation of Islam, and the Black Panther Party.

From 1964 to 1968, Lomax hosted a twice-weekly television program on KTTV in Los Angeles. Lomax also spoke frequently on college campuses.

Lomax was a supporter of several civil rights organizations, including the Congress of Racial Equality (CORE), the Student Nonviolent Coordinating Committee (SNCC), and the Southern Christian Leadership Conference (SCLC).

Lomax died in a car accident when the brakes on his car failed near Santa Rosa, New Mexico. At the time, he was working on a documentary concerning the role played by the FBI in death of Malcolm X. According to Washington Post staff writer Karl Evanzz, Lomax's death may have been connected to the documentary. At the time of his death, Lomax had a 141-page FBI file.