Wind energy from offshore wind turbines is an important part of the renewable energy revolution. Due to their good combination of strength and ductility and their corrosion resistance, duplex steels, such as 1.4462, are mainly used in these systems. Due to cathodic polarization, the material is exposed to the negative influence of hydrogen, which is known as hydrogen embrittlement. The influence of hydrogen on the material is affected by various aspects, such as the hydrogen activity in the environment and the mechanical loads. In addition, microstructural properties such as grain size, phase distribution, or different grain boundary types also influence hydrogen diffusion and mechanical behavior. Therefore, it is necessary to understand the influence of hydrogen on the fatigue behavior of the duplex steels. This requires modeling of both, diffusion and mechanical behavior, at the microstructural level. In this work, the mechanical behavior as the first step toward microstructure-based modeling of hydrogen-influenced duplex steels is addressed. Since hydrogen traps, such as dislocations, can have a significant influence on diffusion kinetics and hydrogen concentration in the material, a non-local gradient-based single-crystal plasticity model is used accounting for geometrically necessary dislocations. A computational model is developed for the analysis of the micromechanical behavior of the two-phase material and the evolution of the geometrically necessary dislocation densities.