A benchmark study is presented of new methodologies of the Studsvik CASMO-4/SIMULATE-3 advanced nuclear design code system against a pressurized water reactor (PWR)-type mixed-oxide (MOX) fuel critical experiment with high plutonium content. Both CASMO-4 two-dimensional transport core calculations and SIMULATE-3 nodal core calculations that use the pin power reconstruction model are performed for the experimental geometries. All the assembly two-group constants for SIMULATE-3, including those for MOX assemblies, are generated by CASMO-4 singleassembly calculations. The CASMO-4 improved transmission probability method and the SIMULATE-3 improved nodal and spectral interaction models are verified to be effective for accurate prediction of the pin power distribution inside high plutonium content PWR MOX assemblies and UO2 assemblies that are adjacent to the MOX assemblies.