Livestock grazing is a common management practice recommended to protect biodiversity of semi-natural grasslands. However, the effects of specific management regimes on species diversity can differ considerably among taxonomic groups. We studied short-term effects of sheep grazing on species diversity of ants. We investigated whether one season of sheep grazing affects the species richness of ants and causes a compositional change in species occurrence. We conducted our study in southern Poland at five Natura 2000 sites that create favourable habitats for thermo- and xerophilic ants. The average number of ant species detected in grazed plots was slightly but insignificantly higher as compared with that in ungrazed ones. Three species were detected only in ungrazed plots. Our results are in accordance with other reports, leading to the conclusion that the variation in ant diversity may be primarily driven by site-specific conditions rather than grazing per se.