Electrocoagulation (EC) has been used to treat a wide variety of wastewaters, including textile, dye, electroplating, chemical mechanical polishing wastewaters, etc. Excessive coagulant material may be avoided by electrocoagulation. The contaminants present in wastewaters are maintained in solution by electrical charges. The metal ions of opposite electric charge, provided by an electrocoagulation system, may become unstable and precipitate in a form that is usually very stable. In the present work, the decolorization of navy blue-3G from synthetic wastewaters by an electrocoagulation method has been studied. In the EC of navy blue-3G, the effect of the initial concentration of dye, type of electrode, voltage, pH, turbidity and time on the efficiency of EC process are tested. The experimental results revealed that the color of navy blue-3G in an aqueous phase is effectively removed up to 95% and 93% with aluminum and iron electrodes, respectively.