The influence of viscoelastic stress relaxation on the curlresponse of paper subjected to transient humidity changes wasinvestigated numerically and experimentally. We considered asymmetrictwo-ply paper sheets consisting of low (L) and high (H) anisotropy pliesbonded together. Experiments were conducted at room temperature atvarious constant relative humidities (RH) to obtain the mechanicalproperties, moisture content, moisture expansion coefficients, andstress relation curves of the constituent plies. The time-dependent curlresponse of an unconstrained sheet was analyzed using finite-elementanalysis. Geometrically linear analysis predicted a double curvatureshape of the sheets while geometrically nonlinear analysis predicted acylindrical (single-curvature) shape with the axis in the direction ofthe major stiffness (MD). The analysis revealed that viscoelasticity haslittle influence on curling in dry conditions. With increased humidity,the moisture absorbed softens the material, reduces the relaxation time,and the curvature response becomes highly viscoelastic. Predictedtime-dependent curvature response was in reasonable agreement withexperimental measurements, although it was observed that the analysisunderpredicted the curvature change during the increasing phase of themoisture loading. Such a deviation is attributed to the assumption ofuniform through-thickness distribution of moisture in the analysis.