We study the percolation model on Boltzmann triangulations using a generating function approach. More precisely, we consider a Boltzmann model on the set of finite planar triangulations, together with a percolation configuration (either site-percolation or bondpercolation) on this triangulation. By enumerating triangulations with boundaries according to both the boundary length and the number of vertices/edges on the boundary, we are able to identify a phase transition for the geometry of the origin cluster. For instance, we show that the probability that a percolation interface has length n decays exponentially with n except at a particular value pc of the percolation parameter p for which the decay is polynomial (of order n −10/3 ). Moreover, the probability that the origin cluster has size n decays exponentially if p < pc and polynomially if p ≥ pc.The critical percolation value is pc = 1/2 for site percolation, and pc = 2