Ferrocene and its derivatives have been extensively used as an internal reference in electrochemical processes. Yet, they possess limitations such as solvent restrictions that require chemical modifications. In this regard, we have studied the use of metallacarboranes [3,3'-M(1,2-C2B9H11)2]- (M = Co, Fe) as general internal reference systems and have proven their suitability by thoroughly investigating their electrochemical properties in both aqueous and organic electrolytes without any derivatization.