Survivin is a mitotic spindle-associated protein involved in linking mitotic spindle function to activation of apoptosis in mammalian cells. The structure of the full-length human survivin has been determined by X-ray crystallography to 2.7 Å. Strikingly, the structure forms a very unusual bow tie–shaped dimer. It does not dimerize through a C-terminal coiled-coil, contrary to sequence analysis prediction. The C-terminal helices contain hydrophobic clusters with the potential for protein–protein interactions. The unusual shape and dimensions of survivin suggest it serves an adaptor function through its α-helical extensions.