A series of large-scale dynamic direct shear tests were performed to measure the interface shear strength between a textured geomembrane (GMX) and a needle-punched geosynthetic clay liner (NP GCL) under cyclic loading. The study was conducted for large ranges of shearing normal stress (σn,s= 13 to 2071 kPa) and cyclic displacement amplitude (Δa = 2 to 30 mm). The experimental data indicate that the failure mode of a GMX/NP GCL specimen depends on both σn,s and Δa. All tests conducted at low to moderate normal stress levels (σn,s ≤ 692 kPa) produced interface failures. Partial to complete internal failures were observed for some tests at low Δa and high σn,s. Interface failures still occurred for the largest displacement amplitude (Δa = 30 mm) at all normal stress levels. In general, the testing program has indicated a more complex interrelationship among failure mode, normal stress level and shear displacement rate than has been previously considered for these materials.