The results of the study of the effect of a mononuclear dinitrosyl iron complex (DNIC7) with functional sulfur-containing ligands (NO donors) on the viability of multiple myeloma cells are presented. It was shown that DNIC7 decreased cell viability and inhibited the proliferation of multiple myeloma cells, i.e., exhibits cytotoxic properties. Fluorescent analysis showed that the DNIC7 compound decreases the level of intracellular glutathione and increases the level of reactive oxygen species in multiple myeloma cells. It is assumed that DNIC7 has a therapeutic potential for the treatment of cancer.