Abstract Self-diffusion of both constituents in the Laves phase NbCo2 has been explored using the tracer method and the radioisotopes 57Co and 95Nb in combination with sputter and grinder sectioning. The temperature dependences of the Co diffusivity in Nb31Co69 and Nb29Co71 (two compositions inside the phase field of NbCo2) and of the Nb diffusivity in Nb31Co69 are reported. All activation enthalpies are of similar magnitude. Nb diffusion in NbCo2 is significantly slower than Co diffusion. Co diffusion itself is considerably faster in the alloy with higher Co content. The diffusion results are discussed in connection with the structure of and the scarce information available about atomic defects in NbCo2. We propose that diffusion is mediated by thermal vacancies. Furthermore, the results are compared with self-diffusion data for the C14-type Laves compounds MgZn2 and Tife2, with interdiffusion data obtained from multiphase diffusion experiments in our laboratory, and with self-diffusion in the also close-packed L12 intermetallics.