In contrast to Mises plasticity, the (classical) crystal plasticity accounts for the underlying crystalline microstructure such as the crystal lattice and the corresponding slip systems. Regarding polycrystals, the overall mechanical behavior is considerably impacted by grain boundaries (GBs), which are represented as material singular surfaces in classical continuum mechanics, cf., e.g., [1]. Regarding the simulation of microstructure evolution, tracking these sharp interface (SI) GBs can prove challenging and costly from a numerical perspective. This issue can be circumvented by implementing the CP in the multiphase-field approach (MPFM) [2]. The MPFM is an effective approach for treating moving surfaces, which are modeled as diffuse interfaces with finite thickness. This talk briefly discusses the implementation of the crystal plasticity within the diffuse interface region [4] using the jump condition approach [3]. Three-dimensional simulations demonstrate the consistency between the MPFM and SI solutions in a bicrystal. In addition, the evolution of polycrystalline microstructures after elastoplastic deformation [5] is discussed as a preliminary measure for modeling recrystallization processes. REFERENCES [1] A. Prahs, T. Böhlke, Contin. Mech. Thermodyn, Vol. 32, 1417–1434, 2019. [2] B. Nestler and H. Garcke and B. Stinner, Physical Review E, Vol. 71, No. 4, pp. 041609 1–6, 2005 [3] D. Schneider, F. Schwab. E. Schoof, A. Reiter, C. Herrmann, M. Selzer, T. Böhlke, B. Nestler, Comput. Mech., Vol. 60 (2), 203–217, 2017. [4] A. Prahs, L. Schöller, F. Schwab, D. Schneider, T. Böhlke, B. Nestler, Comput. Mech., DOI: https://doi.org/10.1007/s00466-023-02389-6, 2023. [5] T. Kannenberg, L. Schöller, A. Prahs, D. Schneider, B. Nestler, Comput. Mech., DOI: https://doi.org/10.1007/s00466-023-02423-7, 2023.