This paper examines the Iranian humorous folktales through two patterns: the role defining function, and the function generating role, taken mostly from some structural-based approaches and models to narrative, Bremond’s (1970) model, among others. The criticism raised against the traditional model such as AT (1928/1961) is that, being mostly based on the Type-Index and Motif-Index, they cannot reflect the different aspects of the humorous folktales in general, and Iranian folktales, in particular, and it is necessary to call for the other more structurally-based models such as those proposed by narrative grammarians like Bremond, who, following Propp’s (1928) Morphology of Russian Folktales, has placed more emphasis on such concepts as the role defining function as well as the function generating role. Having taken the conceptual-empirical framework as its methodology, this paper tries, through redefining such concepts as an anecdote, joke, and tale as well as reviewing AT classification, to apply the role defining function as well as the function generating role on the Iranian humorous folktales with a narrowed focus on the Iranian numskull folktales. In this sense, a humorous folktale will be defined as an independent narrative unit in which a person or a group of people takes the role of a numskull through the functions they perform. In fact, their role defines their function, and their function generates their role.