Deformation behavior of polycrystalline titanium was studied by numerical simulation in the micromechanical and crystal plasticity frameworks. A three-dimensional model of a polycrystalline structure was generated by the step-by-step packing method based on experimental data. The constitutive equations describing the deformation behavior of grains were derived on the basis of crystal plasticity theory, taking into account the specific crystal structure and dislocation glide on prismatic, basal, and pyramidal slip systems in hcp crystals. A boundary value problem of elastic-plastic deformation of model structures was numerically solved by the finite element method. The verification of the developed model was performed by calculating the elastic-plastic deformation of titanium single crystals with different orientations. Using the model, the contribution of different slip systems to the deformation response of a polycrystal was numerically investigated.