The design optimization of floating breakwaters implicates solving an interdisciplinary problem consisting of three models. The first one arises from the interaction of linear waves with a moored floating breakwater with a leeward boundary that is composed of a vertical sidewall representing the quay wall in ports. The second covers the dynamical behaviour of the oscillating structure caused by the incoming waves. These two assemble the hydrodynamic performance of the floating breakwater; while the third concerns its structural mechanics subject to hydrostatic and hydrodynamic forces. The goal of the optimization problem is to design an optimal floating breakwater that can attenuate the waves to the minimum height inside the port and fulfill several constraints related to floating, stability, and structural resistance. The objective function and constraints are expressed in terms of geometrical parameters of the breakwater as mathematical expressions assembled in an optimization algorithm based on the sequential quadratic programming method (SQP). This yields to several optimal structures each corresponding to a specified wave period. Finally, an analysis is performed to determine an optimum structure for a wide range of frequencies.