The aim of this study was to present the synthesis, characterization, and investigation of the antiproliferative activity of new metal N-Heterocyclic Carbene (NHC) salts (1a-c) and their Ag(I) complexes (2a-c). All synthesized compounds were characterized using elemental analysis, LC-MS, FT-IR,H- 1 NMR, and C-13 NMR spectroscopy techniques. Salts and complexes were tested for antiproliferative activities on human breast and prostate cancer cell lines (MCF-7, MDA-MB-23, DU-145) and L-929 normal cells for 24 h, 48 h and 72 h using MTT assays. The Ag(I)-NHC complexes (2a c) showed dose and time-dependent cytotoxic activity against all cell lines. MDA-MB-231 and MCF-7 human breast carcinoma cells were the most sensitive to displaying IC50 lower than 1 mu M at all time points for 2a and 2b complexes respectively. The IC(50)s for Ag(I)-NHC were higher in normal cells especially compared to the breast cancer cells, suggesting that complexes possessed noteworthy selectivity for human breast cancer cells. Complex 2a showed high selectivity (>= 13-fold) for MDA-MB-231 breast cancer cells at all time points. These results also demonstrated that complex 2b has 4-7-fold selectivity against MCF-7 breast cancer cells. (C) 2019 Published by Elsevier B.V.