We present an original surgical technique for identifying the perfusion area of the cystic vein with indocyanine green (ICG) fluorescence imaging and laparoscopic extended cholecystectomy with lymphadenectomy for a 56-year-old woman with diagnosis of clinical T2 gallbladder cancer (GBC). First, we encircled Calot's triangle using the Glissonean approach from the ventral side of the gallbladder plate and then taped the hilar Glissonean pedicles; these were temporally clamped, and ICG was injected into the vein. The perfusion area of the cystic vein was scrutinized, specifically the stained area of the hepatic parenchyma was marked, and extended cholecystectomy was performed along the resection line. Subsequently, we performed lymphadenectomy of the hepatoduodenal ligament to complete the operation. A postoperative histopathological examination revealed moderately differentiated adenocarcinoma with pathological T1bN0M0. Although extended cholecystectomy is currently recommended for clinical T2 GBC, there is no consensus on the definition of the gallbladder bed, and the ideal extent of hepatic resection has, therefore, not yet been determined. In addition, gallbladder bed resection with 2-3 cm of surgical margin is an empirical procedure that lacks scientific verification. Regarding anatomical features, the cystic vein sometimes drains directly into the anterior branch of the portal vein, penetrating the gallbladder plate and Laennec's capsule of the anterior Glissonean pedicle. To address this background, we have developed a technique to identify the perfusion area of the cystic vein to determine the extent of hepatic parenchyma that should be resected during laparoscopic extended cholecystectomy for clinical T2 GBC.