The electrochemical incineration of organic pollutants on a boron-doped diamond (BDD) thin film electrode was examined by bulk electrolysis, and the mechanism of oxidation was investigated. A comparative study with other electrodes such as Pt and glassy carbon (GC) electrodes revealed the superiority of the BDD over these electrodes. The extent of degradation of phenol and formate due to direct oxidation and hydroxyl radical-mediated oxidation were quantified by amperometric measurements. The extent of direct oxidation was found to decrease with increasing potentials due to the competing hydroxyl radical-mediated reactions. The extent of direct oxidation for formate was found to be higher than that for phenol, indicating the probability of higher adsorption of formate on the oxygen-terminated diamond surface. Finally, bulk electrolysis of phenol at the BDD resulted in the complete destruction of phenol to CO2 with a removal efficiency of 96%, indicating the promising use of BDD for electrochemical waste treatment applications.