Based on linear three-dimensional piezoelasticity, a Legendre orthogonal polynomial series expansion approach is used for determining the characteristics of guided waves in continuous functionally graded piezoelectric materials (FGPM) as spherically curved plates. The displacement components and electric potential, expanded in a series of Legendre polynomials, are introduced into the governing equations along with position-dependent material constants so that the solution of the wave equation is reduced to an eigenvalue problem. Our results from a homogeneous anisotropic spherically curved plate are compared with those published earlier to confirm the accuracy and range of applicability of this polynomial approach. Guided-wave dispersion curves for FGPM and the corresponding FGM spherically curved plates are calculated and the effect of piezoelectricity is shown. The mechanical displacement distribution and electric potential distribution are also illustrated. Finally, the influence of the ratio of radius to thickness on the dispersion curves is discussed.