For optimal usage of novel nanostructures in various industrial applications, it is critical to obtain fundamental understanding of the role of various defects during deformation and failure. To investigate mechanical response of nanoscale devices, we recently developed a new modeling for dynamic evolution of various crystalline defects. Especially, it is critical to understand collective behaviors of dislocation as a source of plastic deformation in most crystalline metals. In this study, we employed our defect dynamics model coupling dislocation dynamics (DD) and finite element modeling (FEM), focusing on the role of defect driven deformation and failure, which could provide unique opportunity to consider the governing mechanisms in microstructure, as well as macroscopic mechanical response. Specific applications include the metallic alloy design using nanoprecipitates and the damage evolution during plastic deformation. The developed model could shed light on a new computational design guidelines for enhancing mechanical properties of metal nanostructures through fundamental investigation of “defect-controlled” mechanical behaviors.