Cellular uptake, luminescence imaging and antimicrobial activity against clinically relevant methicillin-resistant S. aureus (MRSA) bacteria are reported. The osmium( ii ) complexes Os( N ^ N ) 3 2+ ( N ^ N = 1-benzyl-4-(pyrid-2-yl)-1,2,3-triazole ( 1 2+ ); 1-benzyl-4-(pyrimidin-2-yl)-1,2,3-triazole ( 2 2+ ); 1-benzyl-4-(pyrazin-2-yl)-1,2,3-triazole ( 3 2+ )) were prepared and isolated as the chloride salts of their meridional and facial isomers. The complexes display prominent spin-forbidden ground state to triplet metal-to-ligand charge transfer ( 3 MLCT) state absorption bands enabling excitation as low as 600 nm for fac / mer - 3 2+ and observation of emission in aqueous solution in the deep-red/near-IR regions of the spectrum. Cellular uptake studies within MRSA cells show antimicrobial activity for 1 2+ and 2 2+ with greater toxicity for the meridional isomers in each case and mer - 1 2+ showing the greatest potency (32 μg mL −1 in defined minimal media). Super-resolution imaging experiments demonstrate binding of mer - and fac - 1 2+ to bacterial DNA with high Pearson's colocalisation coefficients (up to 0.95 using DAPI). Phototoxicity studies showed the complexes exhibited a higher antimicrobial activity upon irradiation with light. Cellular uptake, luminescence imaging and antimicrobial activity of facial and meridional isomers of Os( ii ) triazole-based complexes against methicillin-resistant S. aureus , MRSA.