<p>Biocomposites developed from biogenic products are notable for their high surface area, tunable antimicrobial activity, biocompatibility, and biodegradable properties. <i>C. vulgaris</i> grown in Blue-Green Medium (BG11 medium) was extracted by maceration, and Ag₂O NPs were synthesized from the prepared extract using a green synthesis method. Cellulose was purified from the remaining waste algal biomass after extraction, and a polymeric matrix was formed with PVA, to which the synthesized Ag₂O NPs were added. Comprehensive characterization of the produced biocomposites was carried out using X-ray diffraction (XRD), confirming the crystal structure of cellulose and Ag₂O NPs and their incorporation into the matrix. Fourier transform infrared spectroscopy (FTIR) demonstrated successful interactions between the polymer matrix and Ag₂O nanoparticles. The surface morphology and distribution of the nanoparticles were analyzed using scanning electron microscopy (SEM) and EDX, revealing that the nanoparticles were homogeneously distributed across the film surface. Thermal analyses were also performed using differential scanning calorimetry (DSC). It was observed that the swelling, biodegradation, and thermal properties of the cellulose-PVA composite were improved by the incorporation of Ag₂O NPs into the structure. The cellulose-PVA-2% Ag₂O biocomposite exhibited high antibacterial activity of 98.5% against <i>Staphylococcus aureus</i> and 97.9% against <i>Escherichia coli</i>.</p>