Relationships between the pore size distribution (PSD) of geotextiles and their airentry suction(ψa) were quantified experimentally.The bubble point test (ASTM D6767) estimates the filtration performance of a geotextile as characterized by the PSD. The bubble point test relies on water retention across the geotextile, whereas the ψ_a of a geotextile is the suction required to introduce air into and through the pores of the porous material and can be obtained by measurement of the water retention curve. Although the PSD of soil has been routinely related to the properties of its soil water characteristic curve, there are few published studies that examine the correlation between the geotextile ψ_a andits PSD. Four types of nonwoven geotextiles were investigated. Bubble point tests and hanging column tests (ASTM D6836) were conducted to obtain PSD curves and geotextile water characteristic curves to characterize the unsaturated hydraulic behavior of the geotextiles. The ψ_a of a geotextile decreases with increasing pore opening size, O95,due to the reduction of the water retention surface. Based on the relationship between PSD and the ψ_a, a geotextile PSD coefficient is proposed thatcorrelates AOS with the ψ_a.