The Nanomechanical defect dynamics model has developed to investigate size dependent plasticity by coupling conventional continuum crystal plasticity finite element (CPFEM) with a discrete defect (DD) modeling. While the detailed defect microstructure and short-range interaction is handled by DD framework, the long-range elastic interactions with image stress field are calculated by CPFEM (using commercial package (ABAQUS) with user subroutine), accounting for complex boundary conditions. The proposed model could account for complex multi-physical phenomena, which would play an important role in obtaining a fundamental understanding of deformation mechanism at small scale. Applications of developed concurrent coupled model includes dislocation nucleation at a crack tip, nanoindentation, hydrogen embrittlement at submicron length scale. The developed model will shed light on fundamental investigation of “defect-controlled” mechanical behaviors in crystalline materials, such as plasticity and damage and fracture.