To evaluate the impact of two predominant management types (mowing vs. tilling) in olive groves on plant diversity, we have surveyed olive groves at ten localities in the surroundings of Šibenik (Dalmatia, Croatia). Among the surveyed groves, 12 were managed by tilling and 11 were managed by mowing. Altogether 323 taxa from 207 genera and 58 families were recorded. The families with the highest numbers of taxa were Fabaceae, Poaceae, Cichoriaceae and Asteraceae. Mowed olive groves were significantly richer in flora (280 taxa) in relation to the tilled ones (181 taxa), with 138 taxa in common to the both management types. An analysis of the life forms showed the domination of therophytes (54.18%) and the phytogeographycal analysis showed that the most frequent floral element was Mediterranean (46.13%). Mowed olive groves almost exclusively contained endemic and endangered species while the invasive alien plant taxa were recorded mostly in the tilled olive groves. Mowing seems as much better management practice from the standpoint of the nature conservation. Based on its floristic composition and richness, tillage seems to completely remove the nursing effect that olive groves can provide for the dry grasslands listed in the Annex I of the Habitat Directive, which are otherwise, in open spaces without grazing exposed to disappearing through the process of secondary succession.