This paper reports bi-directional cyclic loading tests carried out to investigate the influence of out-of-plane deformation on in-plane shear resistance of shear-dominant walls. All the specimens reached their maximum capacity at the inter-story drift of 0.5% or 0.75% in in-plane direction. Shear deformation was about 80% of the total in-plane horizontal deformation in all the specimens. The in-plane maximum lateral load resistances of the specimens subjected to bi-directional loading were approximately 8-18% less than that of the specimen subjected to uni-directional loading. A method considering the effect of out-of-plane deformation proposed by the authors can accurately estimate the in-plane maximum lateral load resistances of the specimens subjected to bi-directional loading.