His best-known book is The Secrets of The Federal Reserve, in which he alleged that several high-profile bankers had conspired to write the Federal Reserve Act for their own nefarious purposes, and then induced Congress to enact it into law. David Randall called Mullins "one of the world's leading conspiracy theorists." The Southern Poverty Law Center described him as "a one-man organization of hate".
Eustace Clarence Mullins, Jr. was born in Roanoke, Virginia, the third child of Eustace Clarence Mullins (1899–1961) and his wife Jane Katherine Muse (1897–1971). His father was a salesman in a retail clothing store. He said he was educated at Ohio State University, New York University, and the University of North Dakota, although the FBI was unable to verify his attendance at any of them, with the exception of one summer session at NYU in 1947.
In December 1942 he enlisted in the military as a Warrant Officer at Charlottesville, Virginia. He was a veteran of the United States Army Air Forces, serving thirty-eight months during World War II.
In 1949 Mullins worked at the Institute for Contemporary Arts in Washington, D.C. where he met Ezra Pound's wife Dorothy, who introduced him to her husband. Pound was at the time incarcerated in St. Elizabeth's Hospital for the Mentally Ill. Mullins visited the poet frequently, and for a time acted as his secretary. Later, he wrote a biography, This Difficult Individual Ezra Pound (1961), which literary critic Ira Nadel describes as "prejudiced and often melodramatic". According to Mullins it was Pound who set him on the course of research that led to his writing The Secrets of The Federal Reserve.
Mullins became a researcher at the Library of Congress in 1950 and helped Senator Joseph McCarthy in making claims about Communist Party funding sources. He later stated that he believed McCarthy had "started to turn the tide against world communism". Shortly after his first book, The Secrets of The Federal Reserve, came out in 1952, he was discharged by the Library of Congress.
From April 1953 until April 1954, Mullins was employed by the American Petroleum Industries Committee (APIC). He was cited in 1954 as a "neo-Fascist" by the House Un-American Activities Committee, which noted in particular his article "Adolph Hitler: An Appreciation", written in 1952, in which he compared Adolf Hitler to Jesus and described both as victims of Jews.
In 1956 he sued the APIC for breach of contract, charging that the group had hired him as a sub rosa propagandist to undermine Zionism, but failed to live up to a verbal agreement to pay him $25,000 for his covert services. The APIC responded that Mullins had been hired “as one of several economist-writers in a subordinate capacity", and denied that he had been employed “in any capacity at any time for the purpose he [alleged].″ The lawsuit, like many others filed by Mullins over the years, was eventually dismissed.
In the 1950s, Mullins began his career as an author writing for Conde McGinley’s newspaper Common Sense, which promoted the second edition of his book on the Federal Reserve, entitled The Federal Reserve Conspiracy (1954). Around this time, he also wrote for Lyrl Clark Van Hyning's Chicago-based newsletter, Women's Voice. He was a member of the National Renaissance Party and wrote for its journal, The National Renaissance. In 1995, he was writing for Criminal Politics. Mullins was on the editorial staff of the American Free Press and became a contributing editor to the Barnes Review, both published by Willis Carto's Liberty Lobby.