Previous research in science education reveals that teachers and students use humour when they communicate with each other in a science education context. In this paper we explore consequences of humour for learning in two different contexts of physics education using video-data: a physics classroom in year nine and a group of four undergraduate students learning basic mechanics together. The video data was analysed with practical epistemology analysis (PEA). The findings showed that the participants in situations of cognitive indeterminacy made jokes to clarify how reasoning and actions tallied with the task at hand. These humorous situations positively affected students’ capability to act intentionally towards the aim of the activity and the results show that this way of joking can have positive consequences for student learning. Therefore, humour ought to be viewed as a significant resource for meaning making in the science classroom.