<p>The increasing contamination of water resources by organic dyes and antibiotics poses a significant environmental challenge, necessitating the development of efficient and sustainable remediation strategies. In this study, samarium doped zinc oxide (Sm doped ZnO) nanocomposites were synthesized via a co-precipitation method and thoroughly characterized by X-Ray Diffraction (XRD) and Field Emission Gun Scanning Electron Microscopy (FEG-SEM). In addition, electrochemical impedance spectroscopy (EIS) analysis was performed to investigate the charge-transfer resistance and interfacial electron transport properties of the synthesized samples. The photocatalytic performance of the synthesized nanocomposites was systematically evaluated through the degradation of tetracycline, aspirin, and methylene blue under ultraviolet (UV) irradiation. The results revealed that the 1 mol% Sm doped ZnO sample exhibited superior degradation efficiency for methylene blue, achieving a removal rate of 93.51%. Conversely, the 2 mol% Sm doped ZnO nanocomposite demonstrated the highest photocatalytic activity against tetracycline, with a degradation efficiency of 66.67% and an enhanced reaction rate constant. Surprisingly, Sm doping did not improve the photocatalytic degradation efficiency of aspirin and showed no substantial effect on the overall performance when compared to undoped ZnO. The photocatalytic behavior of Sm doped ZnO nanocomposites showed pollutant-specific improvements: while samarium incorporation enhanced charge separation and suppressed electron–hole recombination leading to higher degradation efficiencies for methylene blue and tetracycline, it did not improve the degradation of aspirin. These findings underscore the potential of Sm doped ZnO nanocomposites as promising photocatalysts for the remediation of water contaminated with organic dyes and antibiotic pollutants.</p>