The goal of this study was to analyze the argumentative strategies used by preschool children in natural situations of interaction in the classroom. Participants 60 children between 3 and 5 years old from a Day Care Center in Mexico City. The research was qualitative and a non-participant systematic observation process was conducted at three moments of the day: the assembly, the pedagogical activity and the free play with toys. The results showed that during conversation with their teachers and among peers, children generated 10 argumentative strategies: reference of authority, description, comparison, analogy, generalization, narration, anticipation, causality, opposition and alternative proposal. These results provide empirical evidence about argumentation in early childhood.