The following study will discuss the notion of symbolic function in Trần Đức Thảo’s (1917-1993) Phenomenology and Dialectical Materialism (1951). According to the author, the symbolic function is an important step in the evolution of animal consciousness: the lived experience of the organism is no longer felt in the internal flow of consciousness, but rather is communicated to others by the behavior. After briefly describing how the symbolic function results from a particular physiological mechanism of outlined actions and nervous sketches, we will deal with the semiotic structure of symbols: the repressed sketched act becomes the expression of the outline of the whole uncompleted behavior that has been inhibited at the level of the nervous system (which Trần Đức Thảo calls “meaning”). This work also interprets Trần Đức Thảo’s semiology in the context of the scientific and philosophical debates of the 1930s and 1940s.