Ice is a challenging material for understanding the overall behavior of polycrystalline materials and more specifically the coupling between elastic and viscous effects during transient creep. At the single crystal level, ice is an hexagonal material with a rather weak elastic anisotropy but with a strong viscoplastic anisotropy. The strain-stress curve of ice single crystals shows a softening behavior depending on the strain-rate. The strong viscous anisotropy of ice gives rise to the progressive development of intergranular and intragranular strain heterogeneities and to stress concentrations which play an important role in the understanding of the creep behavior of ice polycrystals. The single crystal constitutive relations of Castelnau et al [1] are slightly modified here for a better evolution of the reference resolved shear stress on the slip systems and to account for kinematic hardening at the single crystal level. These constitutive relations are then used in a full-field simulation performed by an elasto-viscoplastic FFT-based method. The material parameters of the model are determined by comparison with experimental data available for single crystals as well as for polycrystals.