Engineering applications in neutron scattering started in the 1980s because of the need to quantify residual stress distribution in industrial components. Over the years, the field of engineering applications has expanded dramatically, from residual stress determination, to fundamental studies of deformation behaviors in polycrystalline structural materials, to mechanical response to electric and magnetic fields in function materials, and lately to the dynamics of structure evolution during phase transition or precipitation. In this chapter, the methodology of neutron diffraction as applied to engineering problems is reviewed, and selected examples are highlighted to illustrate the diverse applications. Technical issues and good practice in precise measurements are discussed. An outlook is provided, along with a discussion of the technical challenges.