Fungal infections, such as those caused by Aspergillus, Alternaria, Colletotrichum, Penicillium, and Rhizopus, are considered the major global threat to human life. In seeking a treatment, we synthesized and characterized copper nanoparticles (CuNPs) using Curcuma longa extract. C. longa plant extract has been previously studied and validated for its strong antimicrobial properties. Novel green particles were synthesized in this study using C. longa and copper nitrate. We also investigated antifungal activity through inhibition studies and real-time expression of gene members belonging to the chitin synthase family. Synthesized CuNPs were characterized by ultraviolet-visible spectroscopy, Fourier transform-infrared spectroscopy, X-ray diffraction, and nanoparticle tracking analysis. Gene expression was determined by real-time PCR. The results visibly confirmed the antifungal activity of the synthesized CuNPs against Aspergillus through zones of growth inhibition. The zone diameters were comparable to those of the positive control used in the study. The synthesized CuNPs were 60 nm in diameter and with a resonance peak at 535 nm. The observations of the downregulation of chitin synthase gene members 1, 2, and 3 suggest significant antifungal activity of the synthesized CuNPs. The collective findings indicate the potential value of green-synthesized CuNPs as antifungal agents.