To address the significant issue of wastewater treatment, this research focused on synthesizing PANI@Ce-doped ZnO (PCZ), a ternary heterojunction with varying dopant concentrations. This heterojunction was prepared using an ultrasonic-assisted wet impregnation technique and underwent comprehensive analysis through several techniques, including XRD, UV-DRS, Photoluminescence, FE-SEM, EDAX, FTIR, and Impedance Analyzer. The synergy between the organic and inorganic frameworks resulted in an additive effect on the photocatalyst's degradation efficiency. This was achieved by enhancing its light-absorption properties and tuning the band gap energy. In the photocatalytic degradation process, reactive oxygen species (ROSs), including O2, OH, and h+, played a crucial role in breaking down MB (Methylene Blue) using the PANI@Ce-doped ZnO nanocomposites. Comparing PANI@Ce-doped ZnO with a 1% Cerium concentration (PCZ1) to its counterparts with different dopant concentrations, PCZ1 exhibited significantly elevated photocatalytic activity. This enhancement can be attributed to the improved transfer and separation of photogenerated charge carriers, which resulted from the effective formation of a heterojunction between the two components with a large trapping site.