The purpose of this study was to examine the effects of coordination support (tool support and tutor support) on the development of shared mental models (SMMs) and coordinated action in a computer-supported collaborative learning environment. Eighteen students were randomly assigned to one of three conditions, including the tool condition, the tutor condition, and the control condition (two groups per condition). Groups in the tool condition were given the task management tools; groups in the tutor condition received assistance from a tutor about coordination; and the control groups did not receive any support. SMMs were assessed on a 5-point Likert scale and coordinated action was analysed by examining learners' logfiles. The findings of this study suggest that tool support facilitates the development of SMMs and promotes coordinated action of each group.