In this study, we investigated the green synthesis of ZnO NPs using the aqueous extract of Lupinus albus L seeds and its potential for photocatalytic and antibacterial applications. Phytochemical study of Lupinus albus L seeds extract, results indicated that the presence of phytochemicals such as flavonoids, polysaccharides, and alkaloid, phenolic compounds in the seed extract, which were confirmed by different screening test. Three different ZnO NPs samples were prepared by varying the ratio of seed extract and zinc nitrate salt precursor as ZnO (1:1), ZnO (3:2), ZnO (9:1) ratio and ZnO NPs synthesized without the presence of Lupinus albus L seed extract as a control and their structural properties were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). All ZnO NPs samples exhibited hexagonal wurtzite structure, with sizes ranging from 20.96 nm to 30 nm. ZnO (9:1) and ZnO (1:1) exhibited rod-like shapes and spherical respectively, while ZnO NPs prepared without presence of seed extract had spherical and flake like shapes. The photocatalytic activity of the ZnO NPs was evaluated by the degradation of MG aqueous solution as well as real sewage sample solution collected from Bahir Dar tannery under visible light irradiation. The results showed that ZnO (9:1) and ZnO (3:2) exhibited higher photocatalytic activity with degradation efficiencies of 98% and 97%, respectively, than the ZnO NPs synthesized without the presence of Lupinus albus L seed extract with degradation efficiencies of 89%. The degradation of MG over ZnO (3:2) and ZnO (9:1) was 1.2 and 1.35 times faster than that of the ZnO NPs synthesized without Lupinus albus L seed extract because the extract modified the morphology and crystal size. ZnO (9:1) also showed good reusability, with no significant loss in degradation efficiency after three cycles and ZnO NPs had good efficiency to degraded, the observed absorbance peak from real wastewater sample. The antibacterial activity of the ZnO NPs was assessed by the disc diffusion method against four different bacterial strains. The results showed that ZnO NPs synthesized with Lupinus albus L seed extract exhibited the highest activity against, K. Pneumonia, with an inhibition zone of 15 ± 0.58 mm. The ZnO NPs synthesized without Lupinus albus L seed extract showed lower antibacterial activity with an inhibition zone of 11.3 ±1 mm, indicating the important role of the seed extract in enhancing the activity of ZnO NPs. Our findings suggest that the green synthesis of ZnO NPs using Lupinus albus L seed extract is a promising approach for the development of efficient photocatalytic and antibacterial activity. Key words: Nanoparticle, ZnO NPs, Photocatalytic activity, Antibacterial activities, Lupinus albus L seed