An eco-friendly and affordable green synthetic approach was employed to synthesize ZnO-A and Fe-doped ZnO-A (Fe/ZnO-A) nanoparticles (NPs) using the leaf extract of Aerva lanata to assess their photocatalytic degradation against the major organic dyes Congo Red (CR) and Orange G (OG) under sunlight. FTIR, XRD, UV–Vis, Photoluminescence, SEM, and TEM were used to characterise the products. The results of the above characterisation techniques FTIR, XRD, UV–Vis, and TEM-indicate the formation of ZnO-A and the incorporation of iron ions into the ZnO-A lattice. The strong absorption at 301 nm in the UV region is due to surface plasmon resonance (SPR). The estimated band gap energies of ZnO-A and Fe/ZnO-A are 5.14 and 4.90 eV, respectively. The crystallite sizes of ZnO-A and Fe/ZnO-A nanoparticles were estimated to be 32 and 38 nm, respectively. The nano-hexagonal phase with a wurtzite structure was observed. Morphological analysis confirmed the formation of well-defined rodlike structures, providing a high surface area for catalytic interactions. The reaction kinetics, rate constant calculation, and UV–Vis full-spectrum analysis were analysed for Fe/ZnO-A against the CR dye. The photocatalytic activity results indicate that higher degradation efficiency was observed with Fe/ZnO-A nanoparticles, achieving 99.6 % for CR dyes compared to undoped ZnO-A nanoparticles. These findings highlight the potential of Fe-doped ZnO nanostructures as an eco-friendly, cost-effective material for wastewater treatment. © 2025