The application of the mechanical energy conservation principle sets a dynamical limit to the performances of compliant lever mechanisms endowed with a positive definite strain energy. The limit applies to every linear compliant lever and is given as an upper bound on the product between the static effective gain of the device and its bandwidth. The relevant parameters of this relation are determined only by the structures surrounding the device and not by its design. This result is obtained on the basis of a linear two-port model, with coefficients determined by the static elastic constants of the device. The model and the dynamical limit are validated by multiobjective optimization analysis interfaced with a finite element model of a practical mechanism.