Through SMFS, we uncovered stronger adhesion of anti-HER2VHH-FcK to Trastuzumab-resistant tumor cells compared to Trastuzumab.Furthermore, our findings revealed the high specificity of anti-HER2VHH-FcK for HER2, even on the surface of Trastuzumab-resistant tumorcells, showcasing its potential to target resistant tumors. Here, ERBB2 is linked to neoplasm.