Platelet function defects are frequently found in patients with chronic myeloid leukaemia. Major clinical bleeding, however, is a rare and infrequently reported complication. Platelet function abnormalities have also not been previously correlated with molecular monitoring of BCR-ABL in chronic myeloid leukaemia. We report a case of a patient with major clinical bleeding as a presenting feature of chronic myeloid leukaemia. The patient developed compartment syndrome of the thigh secondary to a haematoma developing after minor trauma. Fasciotomy was complicated by severe bleeding requiring massive transfusion. Haemostasis was only obtained after activated recombinant factor VII was administered. Laboratory investigations revealed a platelet function defect with reduced platelet aggregation to collagen, epinephrine and arachidonic acid. As imatinib therapy commenced, molecular response was associated with near-normalization of platelet function, which subsequently became significantly abnormal with molecular relapse. Electron microscopy demonstrated normal platelet ultrastructure. We conclude that dysregulated Abelson kinase plays a pathogenic role in platelet function defects associated with chronic myeloid leukaemia, and discuss the management of clinically significant bleeding in patients with platelet function defects associated with myeloproliferative disorders.