Bulk and grain boundary diffusion of calcium in yttria fully stabilized zirconia was studied in air in the temperature range from 1100 to 1400°C. Secondary ion mass spectrometry (SIMS) was used to determine the diffusion profiles as average concentration vs. depth in the B-type kinetic region. The obtained results allowed the calculation of the temperature dependence of the bulk diffusion coefficient D and the grain boundary diffusion parameter D′δs. Activation energies of these processes amount to 333 and 367 kJ mol−1, respectively. Diffusion data of calcium were compared to those of titanium obtained previously using the same zirconia material.