A novel biosynthesis approach was used to develop zinc selenite (ZnSeO) catalysts from the plant extracts of Nephrolepis cordifolia (ZnSeO:NC) and Ziziphus jujube (ZnSeO:ZJ) using hydrothermal method. This study investigates the structural, morphological, and optical properties of pure and biosynthesized ZnSeO catalysts. X-ray diffraction (XRD) analysis confirms the presence of an orthorhombic phase in both catalyst types. Fourier transform infrared spectroscopy (FTIR) reveals the incorporation of secondary metabolites in the biosynthesized ZnSeO catalysts, indicating successful green synthesis. Field-emission scanning electron microscopy (FESEM) demonstrates the formation of needle-shaped nanorod morphology in the prepared catalysts. UV-visible spectroscopy shows a red shift in the optical band gap, with values ranging from 2.40 to 1.60 eV for the biosynthesized ZnSeO catalysts, suggesting enhanced light absorption properties. Barrett-Joyner-Halenda (BJH) analysis highlights the significant influence of plant extract on the surface area of the biosynthesized catalysts. The synthesized ZnSeO catalysts were analyzed for the degradation of Oxytetracycline (OTC) and Rhodamine B (RhB) dyes as well as for their antibacterial activity. Notably, ZnSeO:ZJ catalysts demonstrated enhanced OTC degradation (99%) within 100 min. and RhB dye degradation (99%) within 120 min. The improved kinetic energy, effect of pH, catalysis dosage concentration and scavenger performance for ZnSeO:ZJ catalysts against OTC and RhB dyes compared to pure and ZnSeO:NC photocatalysts. ZnSeO:ZJ exhibits improved growth of inhibition zone against bacterial pathogen B. subtilis (3.30 ± 0.00) followed by E. coli (2.73 ± 0.06). This enhanced degradation efficiency is attributed to the presence of secondary metabolites in the Ziziphus jujube plant extract. These results suggest these catalysts could effectively eliminate wastewater contaminants and innovative antibacterial medications, benefiting the pharmaceutical sector.