Background: Although the relationship between collective efficacy and group performance has been frequently investigated, a few studies have investigated the development of collective efficacy. Aim: This paper proposes some determinants of collective efficacy in small university groups. Group level hypotheses and research questions relating collective efficacy to collective cognition activities, task interdependence, self-efficacy for group work, and collective orientation were posited. Sample: The sample comprised 145 university students in 40 work-groups. Method: A two-phase longitudinal design was employed in the context of university student groups. All groups were required to perform interdependent academic tasks. Aggregated variables were used after testing for within-group agreement. Results: The results of multiple regression analysis provided some evidence that the more group members perceived themselves to be interdependent in the early stages of group work and assigned their tasks interdependently during group processes, the more likely they were to develop high collective efficacy in the final stages of group work. Collective efficacy was also related to the group average of self-efficacy for group work especially when task interdependence was perceived to be high. Conclusions: The results suggest that forming groups with capable university students in group work, strengthening university students' perceptions of themselves as interdependent in the early stages of academic group work and assigning interdependent group tasks during group work may contribute to the development of high collective efficacy.