Collision strengths for transitions among the energetically lowest 46 fine-structure levels belonging to the (1s^2^) 2s^2^2p^2^, 2s2p^3^, 2p^4^, and 2s^2^2p3l configurations of Ca XV are computed, over a wide electron energy range below 300Ryd, using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2003, Comput. Phys. Comm., in preparation). Resonances in the threshold region have been resolved in a fine energy mesh, and excitation rates are determined over a wide electron temperature range below 10^7^K. The results are compared with those available in the literature, and the accuracy of the data is assessed.