A detailed floristic study of Kalimnos resulted in the discovery of 232 vascular plant taxa (species and subspecies) that have not been reported previously from the island and are given in the present contribution. As a consequence, the known vascular plant flora of Kalimnos now comprises about 840 taxa. The distribution on the island of each added taxon, as well as its habitat types, are presented. Linum grandiflorum is reported for the first time as an adventive from Greece, Chasmanthe vittigera is reported as new for the Aegean islands, and Amaranthus muricatus and Taraxacum serotinum as new for the E Aegean islands. Some of the added taxa are not common in Greece, in particular Euphorbia valerianifolia, Heliotropium lasiocarpum, Hyoscyamus aureus, Phacelia tanacetifolia and Silene urvillei.