Arabis watsonii (P.H.Davis) F.K.Mey. was initially reported as Thlaspi watsonii P.H. Davis in Flora of Turkey. Although F. K. Meyer transferred this species to Arabis L., this species has been overlooked and treated as Thlaspi L. in relevant literature for Flora of Turkey. In this study this species was evaluated using molecular (nuclear ITS and plastidic trnL-F sequences) and morphological data. Results clearly show that A. watsonii is sister to the A. hirsuta aggregate and its relatives. In conclusion, our results increased the number of known Arabis species in Turkey to 23. Furthermore, detailed description and distribution of the species are given and a new IUCN threat category for A. watsonii is proposed.