Transplantation-associated thrombotic microangiopathy (TA-TMA) is relatively rare and requires immediate intervention to avoid irreversible organ damage or death; however, consensus regarding the treatment approach is lacking. Atypical haemolytic uraemic syndrome (aHUS) is a rare disease caused by dysregulation of the alternative complement pathway resulting in TMA. aHUS is histologically similar to TA-TMA; approximately 60% of TA-TMA patients have complement dysregulation. Eculizumab, a humanized anti-C5 monoclonal antibody, inhibits terminal membrane-attack complex formation and TMA progression. Eculizumab has been successfully used to treat aHUS post-transplant. We present two cases of kidney TA-TMA due to unknown causes, suspected antibody-mediated rejection, or calcineurin inhibitor (CNI)-related toxicity that developed on day 1 or 2 post-kidney transplantation. Low platelet count and haemoglobin level with red cell fragments were detected. Despite steroid pulse, plasma exchange (PE), and intravenous immunoglobulin therapy, TA-TMA did not improve; therefore, eculizumab was administered despite no genetic testing. Laboratory data, including renal function, improved immediately. TA-TMA treatment primarily involves PE initiation or CNI discontinuation; eculizumab can be used to safely treat TA-TMA and then be ceased in the short term. Therefore, eculizumab administration might be beneficial for kidney TA-TMA as early as the diagnosis of refractory to PE.