While technological improvements of the computer supported collaborative learning (CSCL) have been substantial, its nontask social aspect has not received proportional attention. This study investigates the notion of nontask sociability of CSCL, and identifies its relationship with the students' learning outcomes using the case of an Australian postgraduate programme. Learning outcome is defined as a multiple variable consisting of pedagogical affect, student's interest and perceived learning. Five items were identified for operationalising the nontask sociability. These are ‘finding help’, ‘sense of appealing’, ‘sense of boringness’, ‘sense of interactivity’ and ‘sense of frustration’. In addition, a strong relationship was revealed between nontask sociability and learning outcomes which implies that further attention needs to be given to the nontask aspect of the CSCL interactions. Theoretical and practical implications of the findings are then discussed.