Homogeneous redox catalysis, often associated to EC’ mechanisms, is an elegant way to investigate electron transfer processes. Among the electrochemical tools employed to decipher such processes, scanning electrochemical microscopy (SECM) is a powerful technique to unravel complex EC’ mechanisms, especially those involving short life time intermediates. Herein, it is employed to decipher the mediated reduction of 4-nitrobenzenediazonium by the reduced form of a redox mediator, chloranil, electrogenerated at the tip of the SECM. This strategy that relocates the reduction of the aryldiazonium far from the tip surface allows protecting the tip from passivation and producing very reactive intermediates, i.e. aryl radicals, in solution. Combined with simulations, the SECM in the feedback mode allows describing the whole reduction mechanism and evidences the reaction pathway implying reactive radical species issued from the aryldiazonium reduction. Particularly, it is demonstrated that an irreversible reaction occurring between the aryl radical and the redox mediator is a predominant side reaction.