Multiple myeloma (MM) is a proliferation of tumoral plasma cells that is still incurable. Natural killer (NK) cells can recognize and kill MM cells in vitro. However, previous literature suggests an alteration of NK cell function in MM patients. To further evaluate this point, we used multi-parametric flow cytometry to monitor NK cell phenotype in bone marrow samples at diagnosis of MM, taking advantage of the IFM2009 trial and associated samples. Our results show an increase in the frequency of NK cells in MM patients. A detailed analysis of NK cell phenotype showed a decreased expression of terminal maturation markers such as KLRG1 or CD57 and an increased expression of CD56