Natural killer protein 30 (NKp30; also known as natural cytotoxicity receptor 3, NCR3; or CD337) is an Ig-like activating receptor of NK cells regulating the cross talk between NK and dendritic cells. It is expressed on the surface of NK cells, recently-expanded γδT cells, activated CD8 cells, and innate lymphocytes. The extracellular part of NKp30 consists of a single N-terminal Ig-like domain, followed by a distinct 15 amino acids long stalk region proximal to the plasma membrane, which is important for receptor signaling. Further, three specific cellular ligands of NKp30 have been identified. NKp30 binds a member of B7 family, in particular B7 homolog 6 (B7-H6). Interaction of NCR3 with B7H6 leads to activation of NK cells and induces cytolysis of target cells resulting in apoptotic cell death. Another NKp30 cellular ligand, BAG-6 is recruited to the cell membrane and interacts with NKp30 in some tumor cells or under the stress conditions. The most recently discovered NKp30 ligand, galectin 3, expressed on the surface of some tumors, almost completely blocks NK cell cytotoxicity.