AbstractWe have performed creep and stress‐reduction experiments on polycrystalline ice (grain sizes, d ≈ 30 and ≈ 245 µm) in the grain boundary sliding and dislocation creep regimes (stresses σ = 0.5–5 MPa, temperature T = 233 K) to determine the constant‐hardness creep compliance under these conditions. Our results are consistent with a microstructural state‐variable description of dislocation‐effected deformation whose rate is accelerated by grain boundary sliding. The fine‐grained specimens reveal no subgrain boundaries, indicating that the stress‐sensitive microstructural feature upon which the state‐variable behavior is founded may be the dislocation structure of the grain boundaries. Deviations of our constant‐hardness data from the behavior predicted by the state‐variable formulation allow estimation of the viscosity of the grain boundaries, which is ~4.8 × 106 Pa s at this temperature.