Diffuse large B-cell lymphoma (DLBCL) occasionally presents with circulating malignant cells. The clinical characteristics and long-term outcomes of these patients have not been described. Twenty-nine newly diagnosed DLBCL presenting in leukaemic phase were identified between 1996 and 2010, at two institutions. Median age was 48 years, and patients presented with leucocytosis, high lactate dehydrogenase levels, B symptoms, and high International Prognostic Index score. Extra nodal site involvement was observed in all patients and affected the bone marrow (100%), spleen (62%), pleura/lung (41%), liver (21%), bone (17%), bowels (7%) and cerebrospinal fluid (14%). Blood lymphomatous cells co-expressed CD19, CD20, CD22, CD38, CD45, HLA-DR and FMC7 in >90%, and kappa or lambda light chain restriction in >50%. Ninety per cent received rituximab and anthracycline-based chemotherapy. Overall, remission was complete in 54% and partial in 31%; 15% had resistant disease. Median follow-up was 47 months; 13 (45%) patients remain alive in complete remission. Median progression-free and overall survivals were 11·5 and 46·7 months, respectively. In summary, patients with DLBCL in leukaemic phase present with high tumour burden and frequent involvement of extra nodal sites. In this uncommon DLBCL subgroup, anthracycline-based regimens with rituximab are associated with early morbidity and mortality, but yield approximately 50% 4-year survival.