Geosynthetics in the form of three-dimensional geocells has been in use for some time to improve the performance of foundations. A mathematical formulation was developed to predict the behaviour of a rigid strip footing resting on a geocell-reinforced granular layer overlying soft soil. The combined geocell-reinforced granular layer and the soft soil were considered as Pasternak shear layer and a series of Winkler springs, respectively. Both linear and non-linear responses of the reinforced bed were considered in the analysis, which corresponded to low (< 1% of footing width) and high footing settlements (> 1% of footing width), respectively. An iterative finite-difference scheme was employed to obtain the solution for the governing differential equations and the results are presented in nondimensional form. The present model was validated with two independent experimental test data by comparing the load–deformation patterns which indicated good agreement. Combined soil–geocell properties were varied to obtain the improved load-carrying capacity of the reinforced ground. It was found that the shear stiffness of the reinforced granular bed, namely the product of shear modulus and height of the geocell in a granular bed, plays an important role in improving the performance of the reinforced bed. The effect of shear layer width, shear stiffness of the geocell-reinforced ground and ultimate bearing capacity of the soft soil that brings in variation in improvement of the ground were analysed and the results are presented in terms of design charts. © 2014, Thomas Telford Services Ltd . All rights reserved.