Whenever groups form, members readily and intuitively judge each other’s agentic characteristics (e.g., self-confidence or assertiveness). We tested the hypothesis that perceiving others as low in these characteristics triggers agentic interpersonal behavior among perceivers, which benefits their own reputation in terms of agency. We analyzed data from a longitudinal field study (Study 1, n = 109), a multiwave laboratory study (Study 2, n = 311), and a preregistered experimental laboratory study (Study 3, n = 206). In Study 1, low other-perceptions of agency predicted agentic reputations at zero acquaintance and the reception of leadership nominations later in time. In Study 2, low other-perceptions of agency predicted within-person increases in agentic reputations over time. In both studies, effects of other-perceptions on reputations were mediated by hostile-dominant interpersonal behaviors. In Study 3, experimentally induced low other-perceptions of agency did not predict hostile-dominant behavior, which calls for more research on the proposed mechanism. By emphasizing the role of other-perceptions, the current research provides a new perspective on reputation formation and leadership emergence.