The paper deals with the decisionist approach to organization theory and presents the work of American Nobel laureate Herbert Simon as its chief representative. Information is collected from the work written by Simon himself, from books and papers authored by other people, most notably his close associates and critics, as well as Croatian literature dealing with decision-making in organizations and decision-making in general. Although his extraordinary contribution to several disciplines is recognized in the domestic literature, there is no systematic overview of Simon’s work. This paper aims to fill this void. First part of the paper tackles the basic concepts of Simon’s decisionmaking theory: rationality of decision-making and, in particular, bounded rationality, search for a satisfying solution (satisficing), heuristics, and differentiation between programmed and non-programmed decisions. The paper proceeds by presenting Simon’s understanding of decision-making within the organizational setting. It is argued that Simon’s understanding of organizations is anchored in the differentiation between two types of decisions: decision to participate and decision to produce (intraorganizational decisions). Finally, the last part of the paper explores criticism of Simon’s work.