This paper is to introduce cybernetic epistemology, which is one of the nonlinear or circular epistemology and have provided the basis for the development of various theories and models of family therapy. First, the history and the concept of the term cybernetics is briefly described, and then cybernetics is compared with general systems theory. following is the discussion of different levels of cybernetics, i.e., simple cybernetics and cybernetics of cybernetics, and of their major concepts, respectively. the ways in which cybernetic epistemology is applied to family therapy are also discussed in terms of diagnosis of problems, unit of therapy, goal of therapy, and role of family therapist. Finally, some implications for training and educating cybernetic family therapist are discussed.