The aim of this study was to investigate the photocatalytic degradation of the neonicotinoid insecticide acetamiprid in aqueous solution. Experiments were carried out in a 250 mL batch reactor with recirculation of the reaction mixture and using a UVA-LED radiation source with a heterogeneous UVC-modified perlite-based TiO2 photocatalyst. The photocatalytic degradation of acetamiprid was optimized using a Box−Behnken design (BBD) of the response surface methodology (RSM). The variables in the process optimization were catalyst type, volume of the reaction mixture, and light radiation intensity. From the experimental data obtained, the conversions of the photocatalytic reactions, the reaction rate constants, and the mean square deviations were calculated. The experimental results have shown that the conversion of the reaction is significantly affected by the type of catalyst, i.e., the method used to immobilise the photocatalytic layer on the perlite granules. The highest conversions of 48.49% were reached with catalysts obtained by impregnation methods, while the conversions were quite low (8.68%) for catalysts obtained by sol-gel methods. It was also found that the highest conversions were achieved with the highest radiation intensity and the smallest volume of reaction mixture.