The active and inexpensive catalyst cupric oxide (CuO) loaded foliar fertilizer of graphitic carbon nitride (g-C₃N₄) is investigated for biological applications due to its low cost and easy synthesis. The synthesized CuO NPs, bulk g-C₃N₄, exfoliated g-C₃N₄, and different weight percentages of 30 wt%, 40 wt%, 50 wt%, 60 wt%, and 70 wt% CuO-loaded g-C₃N₄ are characterized using different analytical techniques, including powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and ultraviolet-visible spectroscopy. The nanocomposite of CuO NPs loaded g-C₃N₄ exhibits antibacterial activity against Gram-positive bacteria (Staphylococcus aureus and Streptococcus pyogenes) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The 20 μg/mL of 70 wt% CuO/g-C₃N₄ nanocomposite showed an efficiency of 98% for Gram-positive bacteria, 80% for E. Coli, and 85% for P. aeruginosa. In the same way, since the 70 wt% CuO/g-C₃N₄ nanocomposite showed the best results for antibacterial activity, the same compound was evaluated for anti-fungal activity. For this purpose, the fungi Fusarium oxysporum and Trichoderma viride were used. The anti-fungal activity experiments were not conducted in the presence of sunlight, and no appreciable fungal inhibition was observed. As per the literature, the presence of the catalyst g-C₃N₄, without an external light source, reduces the fungal inhibition performance. Hence, in the future, some modifications in the experimental conditions should be considered to improve the anti-fungal activity.