Shear banding is a commonly observed yet complex form of instability in granular media by which the deformation is localized in a narrow zone along a certain path. The aim of this study is to investigate the micromechanics of shear banding using the discrete element method (DEM). For this purpose, a model was developed and calibrated to simulate the macroscale behavior of sand under plane strain conditions. Upon validation against laboratory experiments, two types of confining boundaries, displacement- and force-controlled, were examined to study the kinematics of shear bands. A constant volume test was then used to investigate the evolution of antisymmetric stresses before, during, and after shear band formation. The results indicate that the antisymmetric stresses significantly increase within the shear band throughout the loading history, but may not describe the precursory shear band conditions. The DEM model is shown to properly capture the micromechanics of shear bands.