New dinuclear di(N-heterocyclic carbene) silver(I), gold(I) and gold(III) complexes have been synthesised and their antiproliferative effects towards various cancer cell lines have been screened. The di(N-heterocyclic carbene) ligands have a propylene linker between the carbene moieties and the imidazole backbone has been functionalised with a 1-benzyl- or 1-PEG-1,2,3-triazole ring (PEG=poly(ethylene glycol)) via a CuAAC (copper azido alkyne cycloaddition) reaction. The resulting gold(I) and gold(III) complexes display an antiproliferative activity superior to that of the unfunctionalised pristine complexes together with a higher selectivity towards cancerous cells with respect to healthy cells. The dinuclear di(N-PEGylated-heterocyclic carbene) gold(I) and gold(III) complexes display a high antiproliferative efficiency, both in terms of activity and selectivity, towards various cancerous cell lines. Display omitted •New dinuclear diNHC Ag(I), Au(I, III) complexes have been synthesised.•Ligand precursors were functionalised by click chemistry (CuAAC).•Functionalised Au complexes display high antiproliferative activity and selectivity.•The Au(III) complex quickly reacts with GSH to afford Au(I) complex and GSSG.