In this paper, we use a geometric approach based on the concepts of variational principle and moving frames to obtain the conservation laws related to the one-dimensional nonlinear KLEIN-GORDON EQUATION. Noether’, s First Theorem guarantees conservation laws, provided that the Lagrangian is invariant under a Lie group action. So, for calculating conservation laws of the KLEIN-GORDON EQUATION, we first present a Lagrangian whose Euler-Lagrange EQUATION is the KLEIN-GORDON EQUATION, and then according to Gon¸, calves and Mansfield’, s method, we obtain the space of conservation laws in terms of vectors of invariants and the adjoint representation of a moving frame, for that Lagrangian, which is invariant under a hyperbolic group action.