In this study, electrocoagulation was evaluated for landfill leachate as a complex wastewater. Effects of all significant parameters including inter-electrode gap, current density, electrode material, time, pH, electrode numbers, salinity, and concentration were investigated. This study reports the changing patterns for chemical xxygen demand (COD) removal, temperature, voltage, and pH during EC for both Fe and Al electrodes under different conditions. According to the results, the best COD removals were achieved at shortest inter-electrode distance (0.5 cm), highest current density (1000 A m−2), highest number of electrodes (6 plates), longest time (60 min), and within acidic pH. Furthermore, for different NaCl concentrations (0–16 g l−1), both falling and rising patterns were observed. This study also provides separate results for the effect of operational parameters on pH, voltage, temperature, and energy consumption during EC. With higher inter-electrode distances, voltage and temperature rose to larger values, whereas pH fell. Besides, increases in initial pH caused rises in all voltage, temperature and pH parameters during EC. Experiments also displayed that higher values of voltage, temperature, and pH occurred at larger current densities. Additionally, with time, pH increased to more basic measures, and voltage similarly increased. Results also reported that although addition of NaCl into medium could drop the voltage and temperature, it formed both falling and rising patterns for pH at different NaCl concentrations. Plus, according to the results, voltage, temperature, and pH all experienced rising patterns in accordance with the increase in the number of electrodes. Finally, a comparative study of energy consumption was performed to analyse the operation parametric effect.