After serving in the U.S. Army Air Corps during World War II, Meltzer became a radio writer and a public relations executive. At the age of 39, he decided to begin a career writing history books for adults and young people by working with Langston Hughes on A Pictorial History of the Negro in America (1956). In his obituary, The New York Times noted that Meltzer wrote in vivid, concise prose about slavery, witch hunts, the immigrant experience, the Depression, the Holocaust, the civil rights era, and the labor movement, among many other subjects.
Among the many honors for his books are five nominations for the National Book Award as well as the Christopher, Jane Addams, Carter G. Woodson, Jefferson Cup, Washington Book Guild, Olive Branch, and Golden Kite Award. Many of his books have been chosen for the honor lists of the American Library Association, the National Council of Teachers of English, and the National Council for the Social Studies, as well as for the New York Times Best Books of the Year list.