Little is known regarding the precise role of different subsets of natural killer T (NKT) cells in the immunopathogenesis of cancer diseases, particularly hematopoietic malignancies. Although it is well known that NKT cells counteract tumor immunity, conflicting reports on the role of NKT cells in hematopoietic malignancies support more investigations to clarify the interactions between NKT cells and the tumor. Among the hematopoietic malignancies, B cell malignancies derive from different stages of B cell maturation in which T cells play a pivotal role. There is evidence which implies the protective role of some subsets of NKT cells in solid cancers as well as B cell malignancies. In this review, we will discuss recent advances about the immunobiology of NKT cells and their precise role in the immunopathogenesis and treatment of different B cell malignancies.