Joseph Hersey Pratt was born on December 5, 1872, in North Middleborough, Massachusetts.

He was an American physician and author. He studied at Yale, Harvard Medical School and Johns Hopkins Medical School (M.D., 1898) in Baltimore, where he met and was mentored by Dr. William Osler (1849–1919). In 1902, Pratt spent half a year in the medical clinic of Professor Ludolph Krehl (1861–1937), specialist of the psychosomatic aspects of human illnesses, at Tübingen and at the University of Heidelberg, Germany. Upon his return, he hoped to combine clinical medicine with laboratory research. He opened a small consulting practice in Boston, while working as a low-paid medical clinic assistant at the Massachusetts General Hospital. In 1905, following Dr. Osler’s suggestion, Pratt began a home-treatment programme that included weekly group meetings. In 1927, he became the Medical Director of the Boston Dispensary. Pratt made two significant contributions to American medicine: he originated the medical practice of group therapy; and he helped establish Boston's New England Medical Center. He is the author of several books, e.g., "A Year with Osler, 1896-1897" (1949) and "Fifty Years in Group Psychotherapy, Commemorating the Pioneering of Joseph Hersey Pratt, M.D., 1905-1955" (1955). He also published numerous articles in various medical journals.

In 1909, he married Rosamond Means Thomson (1884–1949). He died on March 3, 1956, in Boston, Massachusetts.