© The International Society of Offshore and Polar Engineers. The global performance of the KRISO square-type semisubmersible multiunit floating offshore wind turbine (MUFOWT) in irregular waves is numerically simulated by using a multiturbine floater-mooring coupled dynamic analysis program. The developed time-domain numerical-simulation tool is extended from the FAST–CHARM3D coupled dynamics program for a single turbine on a single floater. FAST has been developed by the National Renewable Energy Laboratory for years for the single unit. Recently, KRISO has designed and studied a square-type semisubmersible MUFOWT in which four 3 MW wind turbines are installed at each corner of a single floater. Additionally, 24 point-power-absorber-type linear-generator-based wave energy converters are set up, with six wave energy converters at each side of the platform. For verification, KRISO performed a series of model tests for this MUFOWT with 1:50 Froude scale. In this paper, the MUFOWT simulation program is used to reproduce KRISO’s model test results. In the fully-coupled multiturbine/hull/mooring dynamic simulations, the complete second-order difference-frequency wave forces are also included. The analysis results are systematically compared with the model test results, which shows reasonable correlation between them.