Taking phenol as a pollutant model, the role of chloride electrolytes during the anodic oxidations was investigated in a wide range of concentrations (0.1–1000 mM). Experiments were performed with an electrochemical cell containing a boron-doped diamond (BDD) anode and Pt cathode. The influence of the initial chloride concentration on the degradation performance was assessed by comparing both phenol and TOC removal efficiencies at various time intervals. The results revealed that the chloride ions played interesting and important roles during the electrolytic oxidations, and the reaction kinetics and by products might vary from case to case. Thus, we emphasize the importance of operating level selections in BDD technology, especially when high concentrations of chloride electrolytes are present in the bulk solutions.