The present study examined the mediating role of psychological capital in the relationship between ethical leadership and organizational silence. In this descriptive, correlational study the statistical population comprised all school principals in Khorramabad in academic year 2015-2016 (N= 364). The sample which was drawn based on Cochran’s formula and stratified sampling method included 187 individuals. LISREL program was used and the obtained data were analyzed through structural equation modeling (SEM). Results indicated that ethical leadership had direct (β = 0.34) and indirect (β = 0.48) effects on organizational silence (total effect = 0.82). In addition, ethical leadership had direct (β = 0.74) and indirect (β = 0.001) effects on psychological capital (total effect = 0.74). Furthermore, psychological capital had direct (β = 0.65) and indirect (β = 0.001) effects on organizational silence (total effect = 0.65). In this relationship, psychological capital has more statistical power when it enters the equation as the mediator. More specifically, ethical leadership (β = 0.74) can reduce organizational silence (β = 0.34) through the mediating role of psychological capital (β = 0.65) among school principals.