A green, phytogenic and cost effective synthesis of tin oxide nanoparticles (SnO2 NPs) using aqueous leaf extract of Tradescantia spathacea is reported. The structural, surface morphological and optical studies have been performed using X-ray diffraction (XRD), Fourier-Transform Infrared spectroscopy (FT-IR), Scanning Electron microscopy (SEM), UV–visible diffuse reflectance spectroscopy (UV–vis-DRS), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET). XRD pattern shows SnO2 with tetragonal structure of crystallite size ranging 9–22 nm. The FTIR spectra exhibits the presence of hydroxyl groups, amines, alkenes and phenols from the aqueous leaf extract which are responsible for the synthesis of narrow band gap SnO2 NPs. The SEM analysis suggests slight agglomeration morphology with particle size in the range of 46–89 nm. The band gap energy obtained was in range of 2.51–3.3 eV. Photoantioxidant activities of SnO2 NPs in the dark and under visible light illumination were carried out. The SnO2 NPs showed enhanced photoantioxidant activities under visible light irradiation.