Assessing more than 350 hours of direct observations, researchers found interpersonal relationships and behaviors of inpatient medicine teams were associated with complication rates for patients. The presence of trust, defined as a willingness to be vulnerable to others (e.g., an attending on rounds admitting "I don't know"), and the engagement of the entire team in discussions appeared to be particularly important aspects to ensuring patient safety, associated with decreased length of stay and complication rates. This study highlights the importance of relationships and social interactions between inpatient teams, and applies a rigorous analysis method for defining aspects of relationship characteristics. Poor team communication has previously been linked to patient harms in operating rooms and labor and delivery units.