ZnO nanoparticles (NPs) are biosynthesized for the first time with the aqueous wheatgrass extract (WGE) using the solution combustion method. The synthesized nanoparticles were characterized by XRD, SEM, TEM, DLS, TGA, UV‐Vis. and FTIR. The synthesized ZnO NPs were crystalline, having a wurtzite structure, with an average particle size of 25 nm, confirmed from TEM and DLS. The biosynthesized ZnO NPs from WGE has shown excellent activity against Gram‐positive and Gram‐negative bacteria. They also exhibited good antioxidant and anti‐inflammatory activities with IC₅₀ value of 4.63 μg/mL. When treated with MCF‐7 cell lines, these biosynthesized WGE ZnO NPs have shown a remarkable decline in the cell viability with IC₅₀ value of 44.67 μg/mL. Under the visible light, crystal violet and safranin stains have shown excellent degradation at neutral pH without any reductant, indicating that these green WGE ZnO NPs can serve as a potential photocatalyst in treating wastewater effluents.