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, non-judgmental 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; and 3) 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. The 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. Theoretical and practical implications are discussed.