The authors introduce the concept of team mindfulness, defined as a shared belief among team members that their interactions are characterized by awareness and attention to present events, and experiential, nonjudgmental processing of within-team experiences. Team mindfulness is examined as a safeguard against multilevel team conflict transformation processes. Results from three multi-wave field studies validate a team mindfulness instrument and indicate that team mindfulness (1) negatively relates to team relationship conflict, (2) reduces the connection between task conflict and relationship conflict at the team level, (3) and reduces the cross-level spillover of team relationship conflict to individual social undermining. The research contributes to the growing workplace mindfulness literature by conceptualizing mindfulness at the team level and demonstrating its positive effects for team functioning. Results also contribute to research on team conflict and social undermining, showing that team mindfulness is a promising intervention to reduce team conflict and its ill effects.