Reduction of the grain size to less than 20 nm has provided major advances in soft magnetic materials performance, including reduced core losses and coercivities. These promising results have stimulated research efforts, worldwide, in the areas of nanocrystalline alloy design, alloy processing, materials performance evaluation, and transition to various applications. This chapter presents recent advances in nanocrystalline soft magnetic alloy processing methods, phase transformations, microstructure evaluation, magnetic property measurement and analysis, and applications.