As an emerging organic pollutant, microplastics (MPs) pose a serious threat to the water environment and human health. Effective water treatment processes are urgently needed to remove MPs from the aquatic environment. Herein, an electrocatalytic oxidation system with a CeO₂-modified PbO₂ anode (marked as CeO₂–PbO₂) was proposed for the degradation of polyvinyl chloride microplastics (PVC-MPs). When the CeO₂ concentration in the electrodeposition solution was 0.005 M, the obtained CeO₂–PbO₂ electrode had the best electrocatalytic activity due to its denser structure, higher oxygen evolution potential, and more active sites. After 6 h of electrolysis, the weight loss of PVC-MPs at the CeO₂–PbO₂-0.005 anode was 38.67%, greatly higher than 16.67% at the pristine PbO₂ anode. To explore the degradation mechanism of PVC-MPs, the surface morphologies, elemental states, and functional groups of PVC-MPs were compared before and after electrochemical treatment, and the formed intermediates were identified. Experimental results revealed that the PVC backbones were broken, the CC double bonds were oxidized or oxidatively cleaved into small molecules, and the dechlorination reaction occurred in the electrochemical oxidation process. As a result, the particle size of the PVC-MPs decreased significantly, lots of cracks appeared and many small pieces were formed on the surface of the PVC-MPs.