Small-for-size syndrome (SFSS) is a critical complication of partial liver transplantation, particularly in adult-to-adult living donor liver transplantation (ALDLT) using a small graft. Minimally required liver graft size for a successful ALDLT is classically 40% of a standard recipient’s liver volume or 0.8% of recipient body weight. Recent progress in perioperative care and technical improvement push the lower limit of safe graft size to 25% of the recipient’s standard liver volume or 0.6% of the graft versus recipient weight ratio although this is an ongoing debate. The clinical manifestations of SFSS include various symptoms and signs related to graft dysfunction and portal hypertension in patients with small grafts. The risk factors for SFSS include poor preoperative patient condition, including portal pressure, surgical techniques to reduce portal pressure, and graft quality and size. Hence, various approaches have been explored to modulate inflow and pressure to a small graft and to decrease the outflow block to alleviate this SFSS as well as the selection of a patient and graft. Additionally, recent research and efforts to prevent and treat SFSS are reviewed. (Ewha Med J 2022;45(2):29-34)