The title compound, 1-[(C6H5)(2)PAuC1]-2-(C6H5)-1,2-closo-C2B10H10 or [AuC1{(C6H5)(2)P(C8H15B10)}], is the first reported derivative of 1-[(C6H5)2P]-2-(C6H5)1,2-closo-C2B10H10. The conformation of the cage phenyl group is comparable with the parent carbaborylphosphine, however, the (C6H5)(2)PAuCl substituent is less tilted from an idealized radial position on Cl due to a balance between two opposing sets of intramolecular forces. The P-Au-Cl fragment adopts the expected linear geometry.