Professor Feldman has devoted much of his career to the study of Josephus, the Hellenistic Jewish writer of the first century C.E. His critical edition of the text, translation into English, and commentary on Josephus' Jewish Antiquities, Books 18-20, Loeb Classical Library (Harvard University, 1965), was followed by two monumental critical bibliographies, Josephus and Modern Scholarship (1937-1980) (1984), and Josephus: A Supplementary Bibliography (1986), and scores of articles and special studies. He has few peers in this area of scholarship.

Feldman is regarded as one of America's most outstanding teachers; a teacher's teacher who has led many very successful summer seminars for college and university teachers under the auspices of the National Encoument of the Humanities. He has received numerous fellowships and awards from organizations such as the Guggenheim Foundation, the American Council of Learned Societies, the American Philosophical Society, the Memorial Foundation for Jewish Culture, and the American Academy for Jewish Research.