Zinc oxide (ZnO) nanoparticles are multifunctional materials with wide application potential. The aim of this research is to synthesize ZnO nanoparticles utilizing Indigofera tinctoria leaf extract in methanol as an eco-friendly reducing and stabilizing agent. Synthesis was carried out with variations in extract mass, namely 1 g (Z1), 5 g (Z5), and 10 g (Z10) to evaluate the effect of the extract concentration upon the characteristics of the nanoparticles. FTIR, XRD, SEM, XRF, and UV-Vis DRS were used to characterize the samples. FTIR analysis results showed typical ZnO peaks at wave numbers 422-430 cm-1. XRD analysis revealed that the nanoparticles have a hexagonal wurtzite crystal structure with space group P63mc. The crystallite size decreased as the extract concentration increased, amounting to 16.55 nm (Z1), 15.21 nm (Z5), and 13.75 nm (Z10). The band gap energy value increased from 3.19 eV (Z1) to 3.21 eV (Z10), indicating an increase in optical activity at higher extract concentrations. Morphological analysis by SEM showed that all samples exhibited a quasi-spherical shape. EDS characterization revealed that only Zn and O elements were identified. XRF results confirmed the pristineness of ZnO nanoparticles, with a ZnO content of 98.99%. This research provides new insights into the potential use of Indigofera tinctoria leaf extract in the synthesis of ZnO nanoparticles, which can be utilized in various functional material and technology applications. These results also open up opportunities for the development of green synthesis methods for the fabrication of nanomaterials with characteristics that can be customized according to application needs.