Because of the insidious nature of lymphatic metastatic cancer, accurate imaging tracing is very difficult to achieve in the clinic. Previous studies have developed the LARGR peptide (named TMVP1) as a radiotracer for vascular endothelial growth factor receptor-3 (VEGFR-3) imaging in cancer. However, its affinity for the target remains insufficient, resulting in low imaging sensitivity. In this study, we identified a high-affinity VEGFR-3 targeting peptide, named TMVP1446, using a multiplex screening platform. TMVP1446 demonstrated a dissociation constant of 8.97 × 10-8 M. Both in vitro and in vivo assays confirmed that fluorescently labeled TMVP1446 specifically bound to VEGFR-3. In a 4T1-luciferase tumor mouse model, cyanine 7-labeled TMVP1446 effectively discriminated between contralateral normal lymph nodes (c-LN) and cancer-metastatic sentinel lymph nodes (m-SLN). To evaluate the potential of TMVP1446, we developed a novel VEGFR-3 positron emission tomography radiotracer ([68Ga]Ga-DOTA-TMVP1446) for cancer-m-SLN imaging. [68Ga]Ga-DOTA-TMVP1446 accurately detected and assessed the status of lymph node metastasis, even in micrometastatic tumors, in the B16-F10 mouse tumor model. These findings suggest that TMVP1446 has great potential for advancing VEGFR-3 molecular imaging and metastatic sentinel lymph node imaging.