This study investigates the effectiveness of electrocoagulation (EC) and hybrid electrocoagulation-ultrasound (EC-US) processes for treating landfill leachate from Alor Pongsu Landfill and Pulau Burung Sanitary Landfill in Malaysia. The treatment performance of the EC and EC-US processes was evaluated using aluminum (Al) and iron (Fe) electrodes under various operating conditions, including applied voltage (2 - 10 V), inter-electrode distance (1 - 3 cm), and electrolysis time (5 - 30 minutes) in influencing COD removal efficiency from both landfill leachates. The results showed that the hybrid EC-US process significantly outperformed the EC process. Using Al electrodes, the maximum COD removal efficiency reached 95.05% and 96.31% for Alor Pongsu and Pulau Burung leachates, respectively, in the EC-US process, compared to 80.80% and 81.90% in the EC process. Both methods shared optimal operational parameters: 10 V, 2 cm inter-electrode distance, and 25 minutes of electrolysis time. The highest percentage of anode weight loss, 19.4%, and 21.4%, was recorded in the EC-US process using Al electrodes for Alor Pongsu and Pulau Burung leachates, respectively, indicating enhanced coagulant generation. The findings demonstrate that the EC-US process is a promising and efficient approach for improving COD removal in landfill leachate treatment.