Salvia nemorosa L. is an aromatic herb distributed widely in various regions of Iran, and is used in traditional and modern medicine. In the present study, leaf trichome densities and also type were investigated in six populations of the species, because the effective substances of this species exist in essential oil of glandular trichomes. For this, the mature intact leaves of each population were fixed in FAA solution, and then transverse hand sections were double-stained and studied using light microscopy. Leaf indumentum in all of the populations was dense pilose, with the exception of Tehran population that had loose pilose. Thirteen kinds of trichomes were identified, the main of which were peltate and capitate. PCA-biplot showed that each of these populations had prominent trichome trait(s). Furthermore, significant positive/negative correlations were found between some trichome types with main ecological factors of habitat. The studied populations clustered separately in the UPGMA tree, moreover, PCA and also PCO plots produced similar results. Our findings confirmed that ecological parameters of a habitat have strong effects on trichome morphology and density.