Greenslet graduated from Wesleyan University in 1897, and earned both an M.S and the Ph.D. by Columbia University in 1900. In 1901 he moved to Boston, where after working at the Boston Public Library and the "Boston Advertiser", he became an associate editor of the Atlantic Monthly, 1902-07. In 1910, he became a literary advisor and director of the Houghton Mifflin Co. publishing firm, continuing that employment for fifty-two years.
Ferris Greenslet wrote several biographies. He also wrote a collection of reminiscences, Under the Bridge published in 1943. He died in Cambridge, Massachusetts, on November 19, 1959