A cationic poly(ferrocenylboronium) derivative was prepared by postpolymerization modification reaction of poly(ferrocenylbromoborane) (P1) with 4,4'-dinonyl-2,2'-bipyridyl ((R)bipy). The polymer was found to show good stability under ambient conditions and was well soluble in polar organic solvents. Dialysis in MeOH allowed for isolation of a high molecular weight fraction that was further examined. The number-average of repeat units was estimated by GPC analysis relative to PS standards to be n = 17, tind MALDI-TOF analysis confirmed the chemical structure of the polymer repeat units. A characteristic purple color was observed in solution, which is due to charge-transfer from the electron-rich ferrocenyl to the electron-deficient bipyridylboronium moieties along the polymer main chain.