Thermal instability of deep spherical shells made of functionally graded material and surface-bonded piezoelectric actuators is studied in this article. The governing equations are based on the classical shell theory and the Sanders nonlinear kinematic equations. It is assumed that the property of the functionally graded materials varies continuously through the thickness of the shell, according to a power law distribution of the volume fraction of the constituent materials. The constituent material of the functionally graded shell is assumed to be a mixture of ceramic and metal. The analytical solutions are obtained for three types of thermal loadings and constant applied actuator voltage. Results for simpler states are validated with the known data in the literature.