Green nanomaterial-based electrochemical sensors have attracted considerable attention owing to their biocompatibility, cost-effectiveness, and reduced environmental impact. Hydrogen peroxide (H₂O₂), a key biomarker of oxidative stress associated with aging and various pathologies, requires sensitive and selective detection for reliable biomedical diagnostics. In this work, silver nanoparticles (AgNPs) were synthesized via a green route using orange peel extract (OPE) as both a natural reducing and stabilizing agent, and subsequently employed to fabricate a nonenzymatic H₂O₂ sensor based on AgNP-modified screen-printed carbon electrodes (AgNPs/SPCEs). Structural and spectroscopic characterization confirmed the formation of crystalline AgNPs with an average diameter of ∼32 nm. Electrochemical analysis by cyclic voltammetry demonstrated excellent sensing performance, with dual linear ranges (0.5–10 μM and 10–161.8 μM), a high sensitivity of 20,160 μA mM-1 cm-2, and a low detection limit of 0.3 μM, S/N = 3. Amperometric studies demonstrated high selectivity against common interferents such as ascorbic acid, dopamine, glucose, glutamate, and uric acid. The sensor also achieved reliable detection of H₂O₂ in human urine, highlighting its potential for clinical applications. Furthermore, the versatility of the sensing platform was established by immobilizing glucose oxidase onto AgNPs/SPCEs, enabling enzymatic glucose sensing within a physiologically relevant range (3–18 mM). Collectively, these findings establish green-synthesized AgNP-based electrodes as a sustainable, cost-effective, and high-performance platform for the detection of oxidative stress biomarkers and glucose dysregulation in clinical diagnostics.