A fundamental issue for IS academics and practitioners is how collaborative IT tools can be effectively used to improve group work. Collaborative IT tools are integrated sets of IT functionalities that facilitate communication and information sharing among interconnected entities. Integrating the literature on group support systems with recent work on IT capabilities, this paper introduces the construct of collaborative IT tools leveraging capability. It is defined as the ability of groups to effectively use a set of IT functionalities - workspace sharing, conferencing, file sharing, scheduling, chat, email - available in collaborative IT tools to facilitate group work. Collaborative IT tools leveraging capability is proposed to impact group performance. To enhance the group's effectiveness in leveraging collaborative IT tools, we propose a set of antecedents: customization of collaborative IT tools, the group's habit in using collaborative IT tools, the group's perceived usefulness and ease of use of collaborative IT tools, the group member's trust, and environmental uncertainty. Data from 365 group managers support the study's structural model with the antecedents and outcomes of collaborative IT tools leveraging capability at different levels of environmental uncertainty. The paper discusses the study's contributions to understanding the nature of collaborative IT tools leveraging capability, its impact on group work, and how it can be enhanced to facilitate group work. Implications for enhancing group work with the aid of collaborative IT tools are also discussed.