Synthesis of an o-carboranyl derivative of 4-[5-(4-methyl-1-piperazinyl)-2,5'-bi-1H-benzimidazol-2'-yl]phenol (1), a candidate for application in boron neutron capture therapy for cancer treatment, is described. Decaborane was introduced into 3-(p-cyanophenoxy)-1-propyne (11) to form 1-(4-cyanophenoxymethyl)-1,2-dicarba-closo-dodecaborane(12) (12), which was transformed into the corresponding imidate 10 in order to be coupled with 4-cyano-o-phenylenediamine (13) to give 1-[4-(5'-cyano-1H-benzimidazol-2'-yl)phenoxymethyl]-1,2-dicarba-closo-dodecaborane(12) (14). The latter was reacted to the related imidate salt 15 and condensed with 5-(4-methyl-1-piperazinyl)-o-phenylenediamine (6) to the title compound 1-{4-[5-(4-methyl-1-piperazinyl)-2,5'-bi-1H-benzimidazol-2'-yl]phenoxymethyl}-1,2-dicarba-closo-dodecaborane(12) (2).