<p>Fluorescence probes offer a sensitive and selective approach for detecting arginine, a biomarker for various biological processes including cancer detection. This study presents a fluorescence turn-on sensor using Cu²⁺-quenched bovine serum albumin-derived carbon dots (BSA@CDs) for arginine detection. The synthesized CDs exhibited a strong blue fluorescence with a quantum yield of 10.15%. The sensing mechanism involved fluorescence quenching of BSA@CDs by Cu²⁺ through static quenching mechanisms including electron transfer and Förster resonance energy transfer (FRET), followed by fluorescence recovery upon arginine binding. A linear correlation of <i>R</i>^<i>2</i> = 0.99 was observed, with a limit of detection (LOD) of 25.8&#xa0;µM. The method demonstrated high selectivity and stability against potential interfering biomolecules and ions. Furthermore, the developed BSA@CDs/Cu probe was applied to detect arginine in biological samples such as urine and saliva, achieving recovery rates ranging from 86 to 105% at different dilution factors. A paper-based assay using Whatman 40 filter paper was also developed as a proof of concept for potential point of care applications. This study highlights the potential of BSA@CDs/Cu as an efficient, economical, and non-intrusive fluorescent probe for arginine detection, paving the way for improved cancer biomarker screening methodologies.</p>