A detailed flolistic study of the area of Mt Pendelikon in Sterea Ellas, Greece, in 1998–2009 resulted in the addition of 318 specific and infraspecific vascular plant taxa, which are reported here, to a present total of 1080 taxa. At least 41 adventives enriched the vascular plant diversity of the heavily urbanised area significantly as compared to previous sources. For each newly recorded taxon local distribution and habitat types are presented. Morphological, chorological and ecological comments are included where appropriate. Filago aegaea subsp. aristata is reported for the first time from the Greek mainland. Some of the new records are of taxa rare in Greece or of regional endemics and therefore chorologically, ecologically or taxonomically significant, such as Cephalaria setulifera, Chenopodium pumilio, Consolida tenuissima, Iberis saxatilis, Johrenia distans, Malcolmia africana, Muscari armeniacum, Narduroides salzmannii, Onosma kaheirei, Satureja parnassica subsp. hellenica, Silene oligantha subsp. parnesia and Teucrium montanum subsp. helianthemoides.