<p>Rapidly developing sustainability raises concerns about the role of nanoparticles in environmental applications; however, the influence of these nanoparticles on fungal cellulase activity remains unclear. The present research assessed the role of nanoparticles as magnetic iron oxide (Fe₃O₄) and zinc oxide (ZnO) on cellulase activity using two selected fungal species. Two fungal species, <i>Trichoderma parareesei</i> and <i>Aspergillus costaricensis</i>, were studied. A pure fungal culture was cultivated for its cellulase production using rice husk as substrate to check the role of nanoparticles in its hydrolytic efficiency. After 4 days of incubation at a pH of 5 and a temperature of 30&#xa0;°C, the two pure cultures of fungal species proved to be efficient in cellulase activity on rice husk. The cellulase production of <i>T. parareesei</i> using rice husk as substrate was the highest compared to the control and to <i>A. costaricensis</i>. It appeared that nanoparticles significantly enhanced cellulase activity of the two studied fungal species, which are effective in rice husk degradation. The optimal concentration of Fe₃O₄ nanoparticles was found to be 20 ppm for <i>T. parareesei</i> and 300 ppm for <i>A. costaricensis</i>, while the optimal concentration of ZnO nanoparticles was 2.5 ppm and 7.5 ppm for <i>T. parareesei</i> and <i>A. costaricensis</i>, respectively. At these concentrations, maximum cellulase activity using Fe₃O₄ NPs reached 0.244 FPU/mL for <i>T. parareesei</i> and 0.106 FPU/mL for <i>A. costaricensis</i>, revealing 12-fold and fivefold enhancement compared to the untreated control. Additionally, the treatment with ZnO NPs resulted in higher cellulase productivity, reaching 0.203 FPU/mL and 0.111 FPU/mL for <i>T. parareesei</i> and <i>A. costaricensis</i>, respectively.</p>