In this study, the effectiveness of the electrocoagulation (EC) process was evaluated based on the reduction of organic and nitrogenous contaminants in landfill leachate. A three-compartment electrochemical reactor as pre-treatment of stabilized landfill leachate was carried out ahead of biological treatment. The removal efficiencies of COD, BOD, ammonia, and nitrate were analyzed at pH 4, 6, and 8 with the current densities of 20.83 and 29.17 mA cm–2. At pH 4, the highest removal of COD and NH4+ was obtained, i.e., in the range of 72–81% and 43–59%, respectively. The ratio of BOD5/COD was increased after EC, from initially 0.11 to 0.32 at pH 4. In addition, EC effectively removed humic substances in the leachate by targeting a large amount of high molecular weight humic substances, with around 103 kDa. However, the higher removal efficiency observed at higher current density leads to higher specific energy consumption. At a current density of 29.17 mA cm–2, the specific energy consumption obtained in EC was around 10–17 Wh g–1 COD and 99–148 Wh g–1 NH4+. This could be decreased up to 50% at an applied current density of 20.83 mA cm–2 with slightly lower efficiencies.