Geocells are the 3D reinforcement system with interconnected cells filled with soil. They improve the properties of the soil by interlocking, friction, and confinement. The beneficial effects of geocell reinforcement for the strength and stiffness improvement were studied by several researchers. However, not many numerical studies are available for the simulation of geocell reinforced sand in triaxial compression. Due to the complexities involved in modelling of geocells, many of the previous studies modelled geocell reinforced soil systems using equivalent composite approach where the soil filled geocells were represented as soils with improved stiffness and strength properties or by modelling geocells in cylindrical, square or diamond shapes, rather than their actual honeycomb shape. In this study, the finite difference package, FLAC3D (Fast Lagrangian Analysis of Continua in three Dimensions) is used to carry out the numerical simulations. Triaxial compression tests on cylindrical sample of unreinforced sand and sand reinforced with honeycomb shaped geocells are simulated by implementing the actual shape of geocells. Sand is modelled using the Mohr–Coulomb material model. Geogrid structural elements are used to model geocells. The effects of the confining pressure, size of the geocell, its aspect ratio and stiffness of the geocell material on the stress–strain response of the reinforced sand, is studied through a parametric analysis on the validated numerical model. Results from the current study will help us to better understand the behaviour and performance of geocell reinforced sand in many applications including embankments, foundations and retaining walls.