He taught at the University of Nebraska from 1934 to 1947 and the University of Wisconsin–Madison from 1947 until he retired in 1979. He maintained an office in North Hall at UW–Madison through the late 1980s. One newspaper remembered him as "beloved of generations of students who were attracted by his friendliness and charm as well as his intellectual stature." One former student, David Obey, wrote of him, "Anyone who remembers John Houseman’s portrayal of the law professor in "The Paper Chase" will know what Fellman was like – intimidating, tough, clipped, proper, dry, acerbic.”