In recent years, the sentinel lymph node (SLN) concept has been widely investigated in a variety of solid tumors including gastrointestinal (GI) cancer. This chapter reviews the rationale and refined technical aspects for SLN mapping in upper GI cancer for the intraoperative accurate diagnosis of nodal status to perform individualized minimally invasive surgical approaches. We have described the technical details of the procedure as we have performed it in over 350 consecutive patients with esophageal and gastric cancer and introduced pitfalls and issues remaining. The technical details and clinical applications of SLN mapping differfor patients with esophageal cancer and gastric cancer. Radio-guided method with lymphoscintigraphy using radioisotope-labeled colloid (RI) is essential for SLN mapping for esophageal cancer. Selective lymphadenectomy and SLN-targeted chemoradiotherapy would be feasible and beneficial for the patients with esophageal cancer. For gastric cancer, combined method with dye and RI is recommended for stable and accurate sampling of SLN in the laparoscopic setting. Laparoscopic local resection for superficial gastric cancer with negative SN status would be a reasonable and less-invasive novel procedure based on the SLN concept. We can utilize this procedure not only for an accurate staging but also as a great tool to change the patient care of upper GI cancer by individualized minimally invasive treatments.