Fellman was president of the Midwest Political Science Association, 1955–1956, founding editor of that association's "Midwest Journal of Political Science" (now "American Journal of Political Science"), 1957–1959, vice president of the American Political Science Association, 1959–1960; and on the board of editors for "The American Political Science Review" of the received the Governmental Affairs Award from the Social Science Research Council, 1959-1960; senior research Fulbright fellow, Great Britain (London School of Economics), 1961–1962; holder of research grants from the Fund for the Republic, 1957–1958 and the Social Science Research Council, 1959–1960; and recipient of an honorary degree (Doctor of Laws) from the University of Nebraska, 1966.