A mooring system optimization program has been developed to minimize the cost of offshore mooring systems. This paper describes an application of the optimization program constructed based on the recently developed harmony search (HS) optimization algorithm to offshore mooring design which requires significant number of design cycles. The objective of the anchor leg system design is to minimize the mooring cost with feasible solutions that satisfy all the design constraints. The HS algorithm is adopted from a jazz improvisation process to find solutions with the optimal cost. This mooring optimization model was integrated with a frequency-domain global motion analysis program to assess both cost and design constraints of the mooring system. As a case study, a single-point mooring system design of floating production storage and offloading (FPSO) in deepwater was considered. It was found that optimized design parameters obtained by the HS model were feasible solutions with the optimized cost. The results show that the HS-based mooring optimization model can be used to find feasible mooring systems of offshore platforms with the optimal cost.