Starting with the premise that subteam psychological safety (PS) microclimates are vitally important to team behavior yet invisible to team-level PS concepts and measures, we introduce a multilevel theory and model of PS within work teams. We first demonstrate the inevitability and influence of distinct PS microclimates in teams and highlight the limits of current team PS approaches, and then develop a multilevel PS theory using social network methods. We introduce multilevel PS measures and theorize their influence on specific aspects of team and subteam learning and performance outcomes. These include new applications of traditional network metrics (e.g., team PS density, member-only PS density, subteam PS density, and leader PS centrality) and a newly developed multilevel team PS index (mPSi). The mPSi measure synthesizes multilevel leader and member PS influences in a single number to better predict outcomes in teams that engage in multilevel (subteam and intact-team) activity to meet work demands. We employ the new metrics to examine four archetypal team PS structures, contrasting new and current approaches and illuminating the implications of incongruity between subteam and intact-team safety climates. We propose that this multilevel theory extends the team PS literature, effecting far greater understanding and prediction of team outcomes and development, while increasing the number of team PS studies that reach publication.