<p>We consider a simplified strain gradient elastic-plastic model that includes a dimensional dependence associated with the microstructure of an isotropic material. It is assumed that elastic strains and their gradients are described by the equations of the simplified strain gradient elasticity theory. The equations of plastic flow are determined using a dissipative function expressed in terms of plastic strain rates and their corresponding gradients. According to the adopted equations, the elastic-plastic model is enriched with elastic and plastic strain gradients, which extend the modeling capabilities by including the dimensional scale of the material’s internal length associated with elasticity and plasticity-induced dissipation. An alternative approach is used, in which the equations of plastic flow are integrated over the loading stage to obtain the constitutive equations not for increments but for the full components of stresses, strains and their gradients. The peculiarity of the formulated equations is that they are formally similar in form to the equations of the deformation theory of plasticity. This simplifies the analysis of the correctness and application of the obtained equations to solve boundary value problems. The conditions under which the considered elastic-plastic model with a strain gradient does not contradict Drucker’s postulate are determined. A variational formulation of the boundary value problem in a mixed form involving displacements, strains, stresses, and strain gradients is presented. The results of solving the model problem of uniaxial tension in a square plate with a narrow U-tip cutout, within the strain gradient elasticity theory, are presented.</p>