A leader’s expressed humility has a favorable influence on subordinates’ job satisfaction, creativity, and performance. However, we know little about how humility affects one’s same-level coworkers. Shifting focus away from leader’s humility, we suggest that coworker humility can also produce positive effects but has a relationship-specific component. Some coworker relationships are characterized by greater expression of humility than others. Specifically, we hypothesize that when a coworker expresses a uniquely high degree of humility to another coworker (i.e., relationship-specific humility), the latter coworker experiences a uniquely high level of psychological safety (i.e., relationship-specific psychological safety), which in turn leads that coworker to perform better (i.e., relationship-specific performance). Pilot Study 1 (N = 155, in 32 teams, yielding 823 relationship-specific ratings) showed that humility has a substantial relationship-specific variance component, even in unacquainted teams. Pilot Study 2 (N = 180, in 39 teams, yielding 854 relationship-specific ratings) built on these results in a sample of moderately acquainted teams and showed that relationship-specific humility is associated with relationship-specific perceptions of performance. The Main Study (N = 133, in 32 well-acquainted work teams, yielding 555 relationship-specific ratings) tested our full model. It demonstrated that the association between relationship-specific humility and relationship-specific performance is mediated by relationship-specific psychological safety. We discuss how our findings advance humility research in the workplace by showing that a portion of humility expression is relationship-specific and stems from each employee’s unique interaction with another specific person, and that such relationship-specific humility affects relationship-specific performance.