As chip feature sizes shrink to sub-10 nm, cobalt has emerged as a promising material for next-generation interconnects. However, chemical mechanical polishing (CMP) of cobalt presents a significant challenge in achieving high material removal rates (MRR), primarily due to its exceptional hardness and the dense oxide film on its surface. Meanwhile, the dissociation of acidic carboxyl groups of complexing agents under alkaline conditions significantly reduces their complexing ability, requiring the exploration of additives with alternative functional groups to overcome this limitation. This study investigated four eco-friendly complexing agents—glycine, malic acid, citric acid, and ethyl maltol—in addressing these challenges. Remarkably, the slurry with ethyl maltol achieved a high MRR of 221.49 nm/min with extremely smooth surface, especially with green agents. Ethyl maltol primarily reacted with the H 2O 2-induced oxide film, forming a thin, porous layer which could be easily removed by abrasive friction, improving surface smoothness to 0.87 nm. Density functional theory calculations and molecular dynamics simulations confirmed that ethyl maltol’s superior performance results from its high molecular reactivity and strong complexation with cobalt ions. These findings position ethyl maltol as a promising, eco-friendly complexing agent for advanced CMP processes.