In this work, we propose a novel elastoplastic ordinary state-based peridynamic framework for capturing strain localization phenomena in geomaterials, through the integration of the Modified Cam-Clay (MCC) constitutive model with critical state theory. To overcome the limitations of local continuum models in describing strain localization and mesh-dependent responses, integral-type nonlocal formulations for plastic volumetric dilation and preconsolidation pressure are derived based on peridynamic force states and strain energy density. These nonlocal internal variables are employed to characterize the isotropic hardening behavior of geomaterials within a peridynamic setting. Moreover, a consistent scaling law is established to bridge the peridynamic constitutive parameters in the nonlocal continuum with the classical MCC parameters in the local continuum, thereby ensuring theoretical consistency between the two formulations. Within this unified framework, a corresponding nonlocal yield function is formulated together with the associated flow rule and hardening law, providing a consistent extension of the MCC model to the peridynamic framework. The effectiveness of the proposed model is validated through a series of benchmark simulations, with numerical results showing good agreement with finite element simulations, particularly in capturing strain localization behavior and associated stress–strain responses.