The performance of textured geomembranes (GMB) widely used as base and slope liners is rarely studied. The variability of the thickness and defects on the surface of co-extruded textured GMBs result in variability in the mechanical properties across the GMB roll. Therefore, the effect of texturing on the stress crack resistance (SCR) of unaged and aged high density polyethylene geomembranes is studied. The fracture plane of broken geomembrane specimens in notched constant tensile load (NCTL) test is investigated using the environmental scanning electron microscope. The comparison between the crack growth rate estimated by fracture mechanics laws and the SCR estimated in NCTL test shows that the defects and discontinuities on the textured geomembrane surface are the main source of variability of the NCTL results. The big variability of SCR of textured GMBs observed in the current study suggests that a textured GMB should only be used where required for slope stability and not as a base liner.