This review chapter examines the literature on work team effectiveness. To begin, we consider their nature, define them, and identify four critical conceptual issues—context, workflow, levels, and time—that serve as review themes and discuss the multitude of forms that teams may assume. We then shift attention to the heart of the review, examining key aspects of the creation, development, operation, and management of work teams. To accomplish objectives of breadth and integration, we adopt a lifecycle perspective to organize the review. Topics involved in the team lifecycle include: (1) team composition; (2) team formation, socialization, and development; (3) team processes, effectiveness, and enhancements; (4) team leadership and motivation; (5) and team continuance and decline. We characterize representative theory and research, identify thematic limitations, and highlight work that is beginning to push the boundaries on our critical conceptual issues. We also address application concerns where possible. Finally, we close with a discussion that reflects back on the topics, considers the state of progress regarding our critical conceptual themes, and suggests directions for new research to foster continued progress and development.