Optimum design of truss structures under frequency constraints is a complicated highly non-linear optimization problem with nonconvex solution space. In this paper, a hybrid Charged System Search (CSS) algorithm with Migration-based Local Search (MBLS) is proposed for resolving this problem. The CSS algorithm as a developed metaheuristic optimization algorithm is inspired by the governing laws of electrostatics in physics and the governing laws of motion from the Newtonian mechanics. In the proposed hybrid CSS-MBLS algorithm, the convergence speed of the standard CSS algorithm is enhanced by the MBLS mechanism. Numerical results obtained from some design examples reveal the successfulness and effectiveness of the proposed algorithm in solving truss optimum design problem under frequency constraints.