The use of geocells for support of foundations on weak subgrades has been gaining popularity in recent years. Detailed studies were performed in this work through laboratory tests and numerical simulations to investigate the influence of different parameters on the geocell supported foundations on soft subgrades. A series of large-scale laboratory plate load tests were performed on the geocell-reinforced base layer overlying soft subgrade. The soft foundation soil was simulated using blocks of Expanded Polystyrene (EPS) in the laboratory tests for obtaining consistent subgrade conditions between the tests. The numerical analyses were performed in three-dimensional finite difference numerical program Fast Lagrangian Analysis of Continua in Three Dimensions (FLAC3D). The numerical models were calibrated against the data obtained from laboratory tests. This paper deals with investigating the influence of different parameters such as pocket opening size, height and size of the footing on the performance of geocell-reinforced base layer overlying soft subgrade. The provision of three-dimensional cellular reinforcement (geocells) in the base layer has substantially increased the bearing capacity of the pavement section and the optimum aspect ratio of geocell pocket was found to be close to unity. From the parametric study, it is observed that the potential benefits of geocell reinforcement increases with reduction in weld spacing and height of geocell while the influence decreases with increasing loading area for constant height of geocell layer. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG part of Springer Nature.