The fast spread and transmission of the coronavirus 2019 (COVID‐19) has become one of serious global public health problems. Herein, a surface enhanced Raman spectroscopy‐based lateral flow immunoassay (LFA) was developed for the detection of SARS‐CoV‐2 antigen. Using uniquely designed core–shell nanoparticle with embedded Raman probe molecules as the indicator to reveal the concentration of target protein, excellent quantitative performance with a limit of detection (LOD) of 0.03 ng/mL and detection range of 10–1000 ng/mL can be achieved within 15 min. Besides, the detection of spiked virus protein in human saliva was also performed with a portable Raman spectrometer, proposing the feasibility of the method in practical applications. This easy‐to‐use, rapid and accurate method would provide a point‐of‐care testing way as the ideal alternative for current detection requirement of virus‐related biomarkers.