The development of adequate shared understanding of the task is of critical importance to group functioning. Group leaders play an important role in this respect, as a key function of leadership is to shape group members' understanding of their job. In the present study we focus on decision making groups with distributed information and examine how group leaders shape members' mental representations of the group decision task through leadership behavior rooted in their own representations of the task. We propose that the extent to which the group leader has task representations that emphasize information exchange and integration affects group members' task representations, group information elaboration, and decision quality. We tested these hypotheses in an experiment (N = 94 three-person groups) in which we manipulated whether a group leader was present and whether this leader held representations emphasizing information elaboration. Results supported the hypotheses, and suggest that team leaders may play an important role in creating a socially shared understanding of team tasks.