A fully coupled flow-deformation model is presented for the nonlinear cyclic analysis of multiphase unsaturated soils. The coupling between fluid flow and deformation fields is established using the effective stress parameters. The hydraulic hysteresis is accounted for in the model through the effective stress parameters and the soil water characteristic curve. The volume change dependency of the effective stress parameters and the soil water characteristic curve is addressed in the formulation. The elastic-plastic behaviour due to cyclic loading is captured using the bounding surface plasticity. Numerical examples are presented, demonstrating the application of the proposed approach.