Juanita Morris graduated from Berea College (B.A., 1942) and then studied economics at Duke University (M.A., 1944; Ph.D., 1948). She married Clifton H. Kreps, also an economist, in 1944 and taught economics at Denison University (1945–50), Hofstra College (1952–54; now Hofstra University), Queens College (1954–55), and Duke (from 1955). At the latter she became a full professor in 1968 and four years later was appointed James B. Duke professor of economics. She also served as director of undergraduate studies in economics, dean of the women's college and assistant provost (1969–72), and vice president of the university (1973–77).

Kreps's main field of research was the changing role of women in the labour force and its effect on the overall structure of society. Her published works include Sex in the Marketplace: American Women at Work (1971) and Sex, Age, and Work: The Changing Composition of the Labor Force (1975). She also edited Employment, Income and Retirement Problems of the Aged (1963) and Women and the American Economy: A Look to the 1980s (1976).

Kreps was the first woman to sit on the board of directors of the New York Stock Exchange (1972–77), and in 1977 she became the first woman secretary of commerce; she resigned from the cabinet in 1979. She sat on the boards of several major corporations, including J.C. Penney, which established in her honour an annual award for an outstanding professional woman. From 1985 to 1992 she served as the chairman of the board of overseers of the Teachers Insurance and Annuity Association and the College Retirement Equities Fund.