The treatment of C. I. Reactive Yellow M-3RE in an aqueous solution by the electrocoagulation (EC) method using iron anodes has been studied. In the EC, the effect of the removal of C. I. Reactive Yellow M-3RE was proved and the effect of various operational parameters on Color Removal Efficiency (CR) such as current density, initial pH, electrolysis time, and concentration of dye, etc. were tested. The experimental results revealed that the color of C. I. Reactive Yellow M-3RE in aqueous phase was effectively removed (40.9%). A UV-vis spectrum analysis diagram was exhibited in this research and another mechanism for removal of C. I. Reactive Yellow M-3RE was proposed. Power consumption in the EC of C. I. Reactive Yellow M-3RE was also calculated in this paper.