Abstract <p>The intrinsic property of MXenes to adsorb dyes with high Raman scattering cross-sections makes them promising candidates for surface-enhanced Raman scattering (SERS) biosensors. In the study, we report a vanadium carbide MXene (V₂CT_<i>x</i>)-based SERS biosensor tag, V₂CT_<i>x</i>@Thi (thionine)@Au NPs (gold nanoparticles)-Ab (antibody), owing to its large interlayer spacing and superior dye adsorption capacity. The tag V₂CT_<i>x</i>@Thi@Au NPs-Ab was fully characterized and validated, demonstrating a significantly enhanced Raman signal through both electromagnetic and chemical enhancement mechanisms. Using a handheld Raman spectrometer as a readout tool, the developed handheld SERS biosensor was successfully applied for the detection of viral antigens. The biosensor exhibited excellent linearity (1.562–100 nM) and achieved a low limit of detection (LOD) 1.562 nM. Moreover, the biosensor demonstrated good selectivity and stability for detecting the target S protein in saliva samples. Our study highlights the potential of V₂CT_<i>x</i> MXene as a powerful material for handheld SERS biosensors, paving the way for portable and efficient viral diagnostics.</p> Graphical abstract <p></p>