Research investigating the underlying mechanisms and boundary conditions under which leader humility influences employee voice remains underdeveloped. Drawing from approach–inhibition theory of power and leader humility literature, we developed a moderated-mediation model in which personal sense of power (i.e., employees’ ability to influence other individuals such as their leader) was theorized as a unique mechanism underlining why employees feel motivated to speak up under the supervision of humble leaders. Additionally, the cultural value of power distance was proposed to be a relevant boundary condition to influence such relationship. We tested the model using time-lagged supervisor–subordinate matched data. Results of mixed models analyses provided support for our hypotheses confirming that employees’ personal sense of power mediates the relationship between leader humility and employee voice, and such relationship was found to be stronger when employees’ power distance was lower rather than higher.