The synthesis of bioactive CuO/C nano composite using sucrose as a capping agent is achieved through simple green approach via Response Surface Methodology. The synthesis process was done in a green environment which prevents aggregation of sucrose and promotes nanoparticles formation. The innovative approach produces sucrose as a carbon source mediated copper oxide nanocomposites (CuO/C nanocomposite) with the particle size of 50 nm. Additionally, the produced CuO/C nanocomposite were characterized using microscopic techniques like SEM, TEM and spectroscopic techniques like UV–vis and X-ray diffraction. The antifungal activities of CuO/C nanocomposite were tested against Aspergillus niger and Aspergillus flavus species. At 1000 ppm of CuO/C nanocomposite, it showed 70% restraint on A. flavus and 90% hindrance on A. niger. The fungal inhibition mechanism of bioactive CuO/C nanocomposite was discussed in this research article. The particular high antifungal performance of CuO/C nanocomposite was found against Aspergillus niger while compare to Aspergillus flavus fungal strain. © 2019 Elsevier B.V.