Green synthesis is a simple, eco-friendly and emerging approach of synthesizing nanoparticles (NPs) and currently, attracting scientific community from around the world. The objective of the present study was to synthesize green titanium dioxide (TiO2) NPs and evaluate its performance for the photocatalytic treatment of TWW after the secondary (biological) treatment process. TiO2 NPs was synthesized using leaf extract of the biodiesel plant, Jatropha curcas L. in a one-step at room temperature to examine its treatability for tannery wastewater (TWW). Moreover, the green synthesized TiO2 NPs was further characterized by UV-Visible spectrophotometer, Field Emission Scanning Electron Microscopy (FESEM), X-ray Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), Dynamic Light Scattering (DLS), Brunauer-Emmett-Teller (BET) and Barret-Joyner-Halenda (BJH) analysis. Results confirmed the synthesis and anatase phase of the spherical TiO2 NPs and also unfold the presence of phytochemicals in leaf extract, which might involve in the capping/stabilization of NPs. Further, the green synthesized TiO2 NPs was applied for the first time to testify its potential for the simultaneous removal of chemical oxygen demand (COD) and chromium (Cr) from secondary treated TWW. During the photocatalytic treatment of wastewater in a self-designed and fabricated Parabolic Trough Reactor (PTR), 82.26% removal of COD and 76.48% removal of Cr from TWW was achieved upon the treatment with green synthesize TiO2 NPs, and thus, successfully employed for the wastewater treatment. Overall, the green synthesized TiO2 NPs demonstrated the astounding potential for the in-situ treatment of TWW as an alternative clean-green treatment solution.