A new method that utilizes the click cycloaddition reaction to functionalize B12H11SH2- (BSH) with organic molecules was investigated. S,S-Dipropargyl-SB12H11- (1) and S-propargyl-SB12H112- (4) were prepared from [(CH3)(4)N](2)B12H11SH and [(CH3)(4)N](2)B12H11S(CH2)(2)CN (2) with propargyl bromide, respectively. Compound 1 or 4 reacted with various azides with mediation by Cu(II) ascorbate to give the corresponding bis-triazolo BSH derivatives (1-) or monotriazole BSH derivatives (2-), respectively, in excellent yields. The click cycloaddition reaction is very useful not only for the synthesis of various BSH-containing organic compounds for boron neutron capture therapy (BNCT) but also for the visualization of boron clusters in cells. We succeeded in the click cycloaddition reaction of compound 1 with Alexa Fluor 488 azide dye and found that 1 accumulated not in the cytoplasm but in the nuclei of HeLa cells.