The peptides pancreatic polypeptide (PP), peptide YY (PYY), and neuropeptide Y (NPY) share a similar structure, known as PP-fold. Within this family of peptides, NPY, a highly conserved 36-aminoacid residue peptide, is involved in the regulation of a wide range of physiological functions, such as food intake and energy metabolism, as well as in the promotion of some remarkable aspects of tumor progression, including cell proliferation, matrix invasion, metastatization, and angiogenesis. NPY exerts its biological effects through five G-protein coupled receptors, named Y1-, Y2-, Y4-, Y5-, and y6-R, which appear associated with different aspects of oncogenesis. Y1-R seems involved in the modulation of cancer cell proliferation, whereas Y2-R activation appears to promote angiogenesis. The development of NPY receptor subtype selective analogs has helped to elucidate the physiological and pathophysiological role and localization of each receptor and may contribute to a better understanding of the receptor-ligand interaction. The NPY system appears to be variously associated with specific tumors, including neural crest-derived tumors, breast and prostate cancers. In addition to NPY, PYY is also able to affect cancer cell growth in a dose-dependent manner and through Y-Rs. In conclusion, peptides of the NPY family and the related receptors play an important role in the progression of different cancer types, with some molecular specificity according to each step of this process. On this basis, future studies may be directed to the implementation of novel diagnostic and therapeutic approaches targeting this system.