We present a 54-year-old man who underwent human leucocyte antigen-identical sibling nonmyeloablative peripheral blood stem cell transplant for primary refractory T-cell prolymphocytic leukaemia (T-PLL). His clinical course was complicated by fulminant haemolysis and acute renal failure at the time of engraftment because of minor ABO incompatibility between the donor and the recipient. This case highlights the curative potential of nonmyeloablative transplantation for T-PLL as well as the potential severity of immune haemolysis secondary to minor ABO incompatibility.