Adult-to-adult living donor liver transplantation (LDLT) has become an established treatment option around the world. However, small-for-size graft syndrome remains one of the most serious complications affecting transplant outcomes. Excessive portal hypertension and overperfusion have been shown to play a causative role in this graft injury. Recently, portal hypertension per se has been considered detrimental to graft function, and thus to be avoided for successful outcomes after LDLT. We constructed a mesorenal shunt with anastomosis of the inferior mesenteric vein and left renal vein in the case of an LDLT recipient who showed high portal vein pressure after graft reperfusion. The inferior mesenteric vein is close to the left renal vein, and the anastomosis was obtained with relative ease. The shunt was effective in decreasing portal vein pressure, and postoperative graft function was satisfactory. This new method represents an option for attenuating portal hypertension when elevated portal vein pressure is observed in adult LDLT after graft reperfusion.