This study investigates the role conversational humor plays in na English language classroom, in which the researcher was also the teacher. The research orientation is qualitative and interpretative, and the theoretical basis lies on Interactional Sociolinguistics, Conversation Analysis and theories of humor, in order to analyze data constituted by audio-taped classes and field notes. A sociointeractional discourse analysis was done, based on the construct of conversational play frame and intends to notice how these frames are initiated and ended and how they influence social construction of knowledge and the relation established between the participants of the investigated context. The conversational play frames may be initiated and ended not only by the teacher, but also by the students, which demonstrates the influence of the flexible style of the teacher in the humor use in the classroom. The results show that conversational humor is essential to promote involvement and to reduce asymmetry between the participants, and is also an auxiliary in the social construction of knowledge in the target language. The main contribution of this study is the understanding of the role conversational humor plays in classroom interactions, resulting in a better comprehension of the interactions that occur in the educational context.