Continual technology development for fusion has come to rely on the principle of "design by analysis" where advanced finite element analysis (FEA) or finite volume analysis provides insight on the performance of engineered systems. Extensive three-dimensional (3D) computations in fluid dynamics, heat transfer, neutronics, magneto-hydrodynamics and electro-magnetics are involved in an iterative design process for magnets, vacuum vessels and in-vessel components. Many difficulties arose in the integration of computer-assisted design (CAD) packages and the numeric models and results from different FEA codes. Over the last decade, engineers developed a vast array of specialized translators and interpolation programs to deal with geometry, mesh and load transfers between single-discipline codes, often with mixed outcomes. Now, several multiphysics codes that allow calculations on the same mesh and easy transfer of loads and other boundary conditions are emerging in the commercial market. These codes often have a robust library of physics models and solvers that address both steady state and transient phenomena and provide simultaneous solutions to heat transfer, fluid flow and structural mechanics problems. This article reviews three existing design tools, provides some examples of how the multiphysics codes are impacting practical engineering design, and identifies some important gaps that still exist today.