Green synthesis is a simple, non-toxic, economical and eco-friendly approach for the synthesis of nanoparticles (NPs). The implementation of new technologies has led to the new area of nano revolution which unfolds the role of plants in bio-and green synthesis of nanomaterials. The plant extracts employed are neem, lemon grass, aloe vera, Indian gooseberry, etc., focusing on the green chemistry principles. In the present work, NPs of titanium dioxide (TiO2) were synthesized using an aqueous extract of Erythrina variegata leaves as a capping agent. The leaf extract was utilized as a reducing agent for the conversion of metal precursors into metal-oxide NPs. E. variegata-mediated TiO2 NPs were characterized by UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy and morphological studies were conducted by scanning electron microscopy. The UV-Vis absorption spectrum showed an absorption band at 317.6 nm, which supports the formation of TiO2 NPs. The optical band-gap energy was determined to be 2.35 eV. Further characterization by XRD supported the crystallinity and purity of the synthesized TiO2 NPs. These NPs may have effective dye degradation ability. The green-synthesized TiO2 NPs exhibited interesting photocatalytic efficacy on methylene blue dye under UV irradiation (using a multi-lamp photo reactor) and antibacterial activity against pathogenic organisms like Streptococcus, Staphylococcus, Escherichia coli and Pseudomonas aeruginosa.