This study analyses the geocell–sand interface shear behaviour by carrying out various experiments using a large-scale direct shear test setup. Three different PVC polymers were used for fabricating the geocell. Locally available river sand was selected as the base material for experimental investigation. The testing programme mainly includes determining interface shear properties of reinforced and unreinforced sand under three different normal stresses (100 kPa, 150 kPa, 200 kPa). The shear performance of geocell-reinforced sand was investigated in the laboratory by varying the aperture size, height, position, shape and strength of the geocell layer. Experimental results have confirmed that all the parameters considered for the study have a significant role in improving shear parameters at the geocell–sand interface. The geocell-reinforced sand exhibits apparent cohesion, and this apparent cohesion may be interpreted as the cohesion mobilised due to confinement provided by the geocell against lateral movement. The friction angle of geocell-reinforced sand was also improved due to the provision of geocell.