Sinusoidal obstruction syndrome (SOS) is one of the severe complications of hematopoietic stem cell transplantation (HSCT). Systemic management including respiratory and circulatory support is necessary. In addition, abdominal paracentesis is often needed for pain relief and to reduce the pressure of tense ascites. Concentrated ascites reinfusion therapy (CART) involves the filtration, concentration, and reinfusion of drained ascites, which contributes to reuse of autologous proteins. CART has been reported as supportive therapy for patients with liver cirrhosis and cancer. We retrospectively reviewed the efficacy and safety of CART in three patients (two with acute myelogenous leukemia and one with chronic myeloid leukemia) who developed SOS after allo-HSCT. They all had symptomatic, tense, and diuretic-refractory ascites with right costal pain and marked weight gain. Two patients showed immediate improvement after CART. However, one patient experienced four CARTs with slow recovery. All patients are now alive and are being monitored as outpatients over 2 years with remission. No severe adverse event was observed related to CART, and 25.2-98.0 (median 30.2) grams of albumin was collected and reinfused. CART after paracentesis reduces protein loss in ascites by reinfusion of autologous protein instead of exogenous albumin preparations. Although transient fever is reported as a frequent adverse event, no events like severe bleeding or infection were observed. While its safety has not been fully established in patients with hematological disease after HSCT, CART may be a considerable supportive therapy for SOS with tense ascites.