A series of water retention tests were performed for five nonwoven geotextiles of different materials and manufacturing processes. The van Genuchten model was applied to both the water retention curves obtained from these tests and to previously published data. Method of estimating water retention curves of the drainage process using the saturated hydraulic conductivities of nonwoven geotextiles were investigated. The water retention curves during nonwoven geotextiles drainage are S-shaped and are similar to those of soil material. Furthermore, the results also show that the nonwoven geotextile water retention curves can be estimated by the van Genuchten model. This study suggests that drainage phase water retention curves and unsaturated hydraulic conductivities can be estimated by only testing the permeability of saturated nonwoven geotextiles.