A series of novel platinum(II)-2,2':6',2"-terpyridine (trpy) complexes containing (thioalkyl)dicarba..closo-dodecaborane(12) (closo-carborane) derivatives were prepared by treatment of the labile precursor species [Pt(MeCN)(trpy)](OTf)(2) with R(CH2)(n)SH (R = closo-1,2-carborane, n = 0-3; R = closo-1,7-carborane, n = 1; R = closo-1, 12-carborane, n = 1) in the presence of NEt3 to afford brightly colored complexes of the type [PtS(CH2)(n)R(trpy)]OTf. All products were characterized by means of multinuclear (H-1, C-13, B-11, and Pt-195) 1D- and 2D-NMR spectroscopy, ESI-MS, and, for the 1,7-carborane derivative, X-ray crystallography. Preliminary in vitro cytotoxicity studies of selected complexes against human ovarian carcinoma cells are also reported.