Organizing intensive care unit (ICU) interprofessional teams- nurses, physicians, and respiratory therapists -is high priority due to workforce crises but how often clinicians work together (i.e., interprofessional familiarity) remains unexplored. Determine if mechanically ventilated patients cared for by teams with greater familiarity have lower mortality, shorter duration of mechanical ventilation (MV) and greater spontaneous breathing trial (SBT) implementation. Using electronic health records from 5 ICUs (2018-2019), we identified the interprofessional team that cared for each mechanically ventilated patient each shift, calculated familiarity and modeled familiarity exposures separately on ICU mortality, duration of MV and SBT implementation using encounter-level generalized linear regression models with a log link, unit-level fixed effects adjusting for cofounders, including severity of illness. Familiarity was defined as how often clinicians worked together for all patients in an ICU (i.e., coreness) and for each patient (i.e., mean team value). Among 4,292 patients (4,485 encounters, 72,210 shifts), unadjusted mortality was 12.9%, average duration of MV was 2.32 days and SBT implementation was 89%. An increase in coreness and mean team value, by each's standard deviation, was associated with lower probability of dying (coreness, adjusted marginal effect (AME) = -0.038, 95% CI (-0.07, -0.004); mean team value, AME=-0.0034 (-0.054, -0.014), greater probability of receiving SBT when eligible (coreness, 0.45, (0.007, 0.083); mean team value, 0.012 (-0.017, 0.042)) and shorter duration of MV (coreness, -0.23 (-0.321, -0.139)). Interprofessional familiarity was associated with improved outcomes; assignment models that prioritize familiarity might be a novel solution.