Evernia prunastri (L.) Ach. (Parmeliaceae), an edible lichen commonly known as oakmoss, was traditionally used by Egyptians to make bread. In this study, the ethyl-acetate (EtOAc) extract of E. prunastri was investigated for its potential therapeutic applications in diabetes mellitus, Alzheimer’s and Parkinson’s diseases, oxidative stress, and bacterial infections. The extract exhibited significant in vitro enzyme inhibition activities, including anti-amylase and anti-glucosidase activities linked to diabetes and anti-cholinesterase and anti-tyrosinase activities associated with Alzheimer’s and Parkinson’s diseases. The antioxidant activity was evaluated through multiple assays, including free radical scavenging (DPPH and ABTS), reducing power (CUPRAC and FRAP), metal chelation, and phosphomolybdenum methods, demonstrating strong oxidative stress relief potential. The antibacterial properties were also confirmed through antibacterial testing, showing efficacy against a range of bacterial strains. Total phenolic and flavonoid contents were quantified, while the chemical profile of the EtOAc extract was determined by LC-HRMS/MS analysis. The chemical composition was predominantly characterized by depsides (evernic acid and atranorin), phenolic acids (orsellinic acid), and dibenzofurans, revealing a diverse array of bioactive secondary metabolites. The extract demonstrated a broad spectrum of biological activities, including enzyme inhibition, antioxidant effects, and antibacterial properties. This study highlights the potential of E. prunastri as a functional food, providing a rich source of bioactive compounds with numerous health-promoting effects, and it suggests its relevance in therapeutic applications for chronic diseases such as diabetes, Alzheimer’s, and bacterial infections. Keywords: Evernia prunastri; phenolics; enzyme inhibition; antioxidant activity; antimicrobial activity; cookies.