The biosynthesis of nanoparticles as a green synthesis method is a simple, non-toxic, economical and eco-friendly approach to the synthesis of nanoparticles. In this research, nanoparticles of titanium dioxide (TiO₂ NPs) were synthesized using an aqueous extract of Juglans regia (J. regia) green husk. Walnut green husk is an agricultural waste that could be a rich source of valuable compounds. The potential of this low-cost natural material as a source of phenolic compounds with antiradical and antimicrobial activities has been demonstrated by several studies. The UV-vis spectroscopy, X-ray diffraction, FT–IR spectrum, dynamic light scattering, and field emission scanning electron microscopy (FESEM) analyses were carried out to characterize the NPs. The UV–visible spectrum shows a strong absorption peak at a wavelength of 330 nm. The synthesized TiO₂ nanoparticles have anatase phase with an average size of 20–37 nm. The Ti-O bonding was recognized by FTIR analysis. The spherical surface morphology and their Ti and O elemental configurations were characterized by FESEM and EDX respectively. TiO₂ NPs are considered extremely valuable nanomaterials because of their nontoxicity, high stability and photocatalytic activities. Therefore, TiO₂ NPs are useful in cosmetics, chemical sensing, wastewater treatment, antimicrobial applications, hydrogen production and lithium-ion batteries.