Nuclear factor κB (NF-κB), including RelA, RelB, c-Rel, NF-κB1, and NF-κB2, plays a crucial role in immune response, inflammatory reaction, tumorigenesis, and development of peripheral lymphoid organs and lymphocytes. There are two NF-κB activation pathways: canonical pathway (classical pathway) and noncanonical pathway (alternative pathway). Previous studies focused on the effects of the canonical NF-κB pathway (mainly p50-RelA) in hematological malignancies. Recently, the noncanonical NF-κB pathway (mainly p52-RelB) is gradually taken importance in pathogenesis of hematological malignancies. Understanding the relations of the noncanonical pathway with hematological malignancies would provide a new therapeutic approach for these diseases. This review focuses on the noncanonical NF-κB signaling transduction pathway and its relation to hematologic malignancies.