The aim of the study was to explore the types and sources of positive emotions experienced by first year university students studying to become primary school teachers, during collaborative science learning. Fun science activities, designed to enhance students' motivation for science, provided the context for examining the relationship between group members' shared positive emotions and their engagement in collaborative learning of scientific concepts. Data for this study were: self-reports of emotions in several activities (class) and video footage of groups' interactions with follow-up interviews (selected groups). The identification of distinct types and sources of emotions supported Fredrickson's (1998, "What Good are Positive Emotions?" "Review of General Psychology" 2 (3): 300-319) case for distinguishing between joy-related and interest-related positive emotions. Students' emotional experiences and degree of subsequent engagement in collaborative learning of scientific concepts appeared to be influenced by the characteristics of the groups and of the activities (e.g. if competitive). The critical importance of harnessing joy-related emotions and promoting interest-related emotions in collaborative science learning is highlighted.