A method of vector magnetometry, implemented using a single NV–13C spin system in a diamond, is proposed. The method is based on a priori knowledge of the hyperfine interaction characteristics and on the presence of experimentally measured line positions in the optically detectable magnetic resonance spectrum of such a system. The method was experimentally tested on the NV–13C system, in which the 13С atom is located in the third coordination sphere of the NV center.