An investigation of why 1‐aminophenazine fails to form a diazonium salt which will couple with β‐naphthol revealed that the phenazine‐1‐diazonium cation reacts rapidly with water to give l‐diazo‐2(lH)phenazinone (1), whose coupling ability has been demonstrated to be very weak. A similar reaction occurred with 2‐aminophenazine.