To evaluate the efficacy of eculizumab in treating hematopoietic stem cell transplantation-associated thrombotic microangiopathy (TA-TMA) . This retrospective study included 11 patients who developed TA-TMA after allogeneic hematopoietic stem cell transplantation and subsequently received eculizumab treatment at Peking University People's Hospital between June 2018 and May 2024. The incidence of TA-TMA, treatment details, and clinical outcomes were analyzed. Among the 11 included patients [4 males, 7 females; median age: 29 years (range: 9-56) ], underlying diseases were severe aplastic anemia (SAA) in 5 patients, acute lymphoblastic leukemia (ALL) in 3 patients, and acute myeloid leukemia (AML) in 3 patients. The median time to TA-TMA diagnosis was 48 days post-transplantation (range: 4-213 days), and all patients met the diagnostic criteria for high-risk TA-TMA. The median interval from TA-TMA diagnosis to the initiation of eculizumab treatment was 12 days (range: 1-56 days). Patients received a median of 3 doses of eculizumab (range: 1-14). Ten of the 11 patients were assessed as having no response (NR) to eculizumab at the end of treatment or at death. One patient achieved a partial response (PR) but subsequently died after TA-TMA relapsed due to infection. At the last follow-up, all patients were either lost to follow-up or had died. The median follow-up duration was 88 days (range: 33-326 days), and the median time from TA-TMA diagnosis to the last follow-up was 31 days (range: 21-113 days) . Eculizumab demonstrated poor efficacy in this TA-TMA cohort. This might be attributable to the critical and complex condition of the patients, delayed initiation of eculizumab treatment, and insufficient dosage.