The functional profile of natural killer (NK) cells has been reported to be lower in auto-immune haemolytic anaemia (AIHA). In this study, we report a comparative analysis of peripheral blood mononuclear cells (PBMNCs) and the in vitro expansion of NK cells in a patient with AIHA and cancer, with that of other cancer patients without AIHA. PBMNCs and in vitro NK-cell expansion of a 64-year old female patient with ovarian cancer and AIHA was compared with that of four other patients with cancer without AIHA who underwent autologous immune enhancement therapy (AIET). The NK cells were cultured using autologous plasma without feeder layers. The quantities of PBMNCs, NK cells and CD3-CD56+ cells were compared. The average quantity of PBMNCs per ml in Cases I to V were 10.71, 39.2, 49.26, 65.16 and 49.33×10(4), respectively, and the average maximum count of NK cells was 3.9, 1730.03, 1824.16, 1058.61 and 761×10(6), respectively. The average percentage of CD3-CD56+ cells in Cases I to V following in vitro expansion was 1.2, 65.7, 28.63, 65.9 and 40%, respectively. In the present study, probably the first in the literature, the in vitro expansion of NK cells was found to be significantly lower in the AIHA patient. Previously, only a lower NK-cell functional profile was reported. Further studies are required to establish the association between AIHA and NK-cell profile and in vitro expansion, and to find common antibodies between red blood cells (RBCs) and NK cells.