Abstract <p>Green synthesized silver nanoparticles with plant extracts have easy production procedures, raw material usages, low toxicity and high biological activity. It is also possible to recovery the bioactive components contained in plant wastes for use in green synthesis for a sustainability environment. In this study, the waste walnut outer membrane was used in the green synthesis of silver nanoparticles (WO-AgNPs). The WO-AgNPs were characterized by UV-Vis spectrophotometer in terms of color changes, scanning electron microscopy (SEM) was used to determine particle size and Fourier Transform Infrared Spectroscopy was to determine functional groups. The antioxidant activity and inhibition of clinically important enzymes such as α-amylase and α-glucosidase for Diabetes mellitus and acetylcholine esterase for Alzheimer were determined. A maximum peak at 420 nm was detected in UV-Vis analyses and the particle size was determined as 33 nm in average. The DPPH^• radical activity scavenging and iron reducing capacity (FRAP) of the WO-AgNPs were calculated as 92.30 ± 0.89 and 77.51 ± 1.18%, respectively. The inhibition of α-amylase, α-glucosidase, and acetylcholine esterase enzymes was 86.14 ± 1.15, 80.41 ± 2.03, and 83.68 ± 0.94%. The data show that the waste plants could be used in the green synthesis of silver nanoparticles and the WO-AgNPs had potential as enzyme inhibitor in the treatment of Diabetes mellitus and Alzheimer and they were a good antioxidant agent.</p>