In this study, successful synthesis of ZnO nanoparticles (NPs), CuO NPs, and ZnO/CuO nanocomposite through an eco-friendly method using Corriandrum sativum leaf extract as a capping agent is reported. Using XRD, FTIR, UV-Vis, and SEM techniques, the synthesized materials were characterized for structural analysis, functional groups identification, spectroscopic measurements, and morphological analysis. The percentage composition and purity of the samples were determined by using Energy Dispersive X-ray (EDX), which showed the synthesis of materials. Morphological analysis was done by Scanning Electron Microscopy (SEM) which reflected that the CuO NPs, ZnO NPs and ZnO/CuO nanocomposite were spherical, and the average size calculated by using Image J software was around 25 nm, 55 nm, and 11 nm, respectively. FTIR and UV-Vis analyses were used for synthetic confirmation through characteristic peaks of materials. The synthesized (ZnO, CuO, and CuO/ZnO) nanomaterials were evaluated for photocatalytic activity using methylene blue (MB) dye. Among all three photocatalysts, the composite showed maximum photodegradation compared to the other two materials. The present work could lead to a pathway for the decontamination of harmful dyes of wastewater released from different industries.