In this study, the transient response of a semi-infinite crack subjected to dynamic anti-plane concentrated loading in a hexagonal piezoelectric medium with vacuum boundary conditions is investigated. Two useful fundamental solutions are derived and the solutions can be determined by superposition of the fundamental solutions in the Laplace transform domain. The proposed fundamental problems are the problems of applying exponentially distributed traction or electric displacements (in Laplace transform domain) on the crack faces. The Cagniard-de Hoop method of Laplace inversion is used to obtain the transient solutions in time domain. Exact transient Full-Field solutions and exact transient solutions of intensity factors to the problem are both derived. Finally, numerical results are evaluated and discussed in detail.