Water contamination by organic dyes and nitro compounds poses a significant environmental threat, particularly from industrial wastewater discharges. Metal and metal oxide nanoparticles are viable solutions to tackle the increasing global demand for in situ wastewater treatment and recovery. This study explores the use of kaolin-supported metal and metal oxide nanoparticles (Ag, Cu, and CuO NPs) as highly efficient, cost-effective, and environmentally friendly catalysts for the degradation of toxic organic pollutants such as methylene blue (MB) dye and 4-nitrophenol (4-NP) from aqueous solutions. The kaolin-supported silver and copper nanoparticles were synthesized by a two-step adsorption-reduction method, and the CuO/kaolin nanocomposite catalyst was fabricated by a simple wet precipitation followed by a calcination procedure. The synthesized materials were characterized by using advanced spectroscopic and microscopic methods, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-Vis) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and Brunauer–Emmett–Teller (BET). The characterization results confirmed the successful synthesis of the NPs on the kaolin sheets. The fabricated catalyst’s catalytic performance was evaluated by using the reduction of MB dye and 4-NP in the presence of NaBH4 and the oxidation of MB dye by NaOCl as model reactions. Accordingly, the Ag-NPs/kaolin composite exhibited superior catalytic activity in the reduction of MB dye, achieving more than 97% removal after five cycles, with a high reduction rate constant (kred = 0.86 min−1). In addition, the Cu/kaolin nanocomposite showed the highest catalytic activity for 4-NP reduction, with a reduction efficiency of over 99% within 4 min with an apparent rate constant, kapp, of 1.23 min−1. Both catalysts demonstrated exceptional stability and reusability, making them effective materials for long-term water treatment applications. The CuO/kaolin nanocomposite achieved greater than 99% 4-NP conversion within 6 minutes, with a rate constant of 1.76 min⁻¹. The CuO/kaolin nanocomposite was also explored for the oxidative degradation of xxvi MB dye and showed a high degradation efficiency of 98.98% within 6 minutes, with a rate constant of kapp = 0.68 min−1. Thermodynamic parameters revealed that the degradation process was endothermic and spontaneous. In both cases, the CuO/kaolin catalyst showed excellent reusability over seven cycles without significant loss in catalytic performance, indicating its potential for industrial-scale applications. In summary, the obtained results confirm pretty good catalytic activity of the kaolin supported Ag, Cu, and CuO nanoparticles for degradation of model pollutants (methylene blue and 4-nitrophenol) from water solutions. This class of catalysts represents one of the promising cost-effective and environmentally benign options for remediation applications related to wastewater treatment. These easily prepared methods and high efficiency demonstrate the great promise these materials have for applications such as sustainable alternatives to conventional catalysts made from novel metals and other synthetic support materials. Consequently, this work contributes not only to the advancement of heterogeneous catalysis but also offers one practical approach toward solving water pollution challenges using locally available natural resources and low-cost nanoparticle